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i
IMPACT OF CLIMATE CHANGE ON THE OUTBREAK OF
INFECTIOUS DISEASES AMONG CHILDREN IN BANGLADESH:
IT’S PREVENTION AND CONTROL
Authors
Dr. Md. Redwanur Rahman and Dr. A K M Kamruzzaman
ii
Acronyms and Abbreviation
ADB : Asian Development Bank
ARI : Acute Respiratory Illness
BBS : Bangladesh Bureau of Statistics
BCAS : Bangladesh Center for Advanced Studies
BMD : Bangladesh Meteorological Department
CCC : Climate Change Cell
CDMP : Comprehensive Disaster Management Programme
CES : Coverage Evaluation Survey
DGHS : Director General of Health Service
FGD : Focus Group Discussion
GoB : Government of Bangladesh
GFDL : Geophysical Fluid Dynamics Laboratory
IgM : Immunoglobulin ‘M’
IPCC : Intergovernmental Panel on Climate Change
LGED : Local Government and Rural Development
MDGs : Millennium Development Goals
MIS : Management Information System
MOEF : Ministry of Environment and Forest
NGO : Non Government Organization
PPS : Population Proportionate to Size
SEARO : South East Asia Regional Office
UHC : Upazila Health Complex
UNFCC : United Nation Framework convention on Climate Change
UNEP : United Nations Environmental Programme
VBZD : Vector Borne Zoonotic Disease
WB : World Bank
WHO : World Health Organization
WMO : World Meteorological Organization
iii
Abstract
The impact of climate change and global warming are worldwide and global
concern. Climate change related events like temperature, rainfall, humidity,
cyclone etc. have direct and indirect adverse impacts on the outbreak of
infectious disease among children. WHO demonstrates in a report estimates
that more than 33% of disease in children under the age of 5 is caused by
environmental exposures. Infectious diseases continue to be the major cause
of morbidity and mortality worldwide. Bangladesh is unfortunately home to
many infectious diseases. In the most recent national demographic and
health survey (year 2011) 62% of deaths among children under the age of 5
years in Bangladesh were ascribed to infectious diseases. A number of water,
air and vector borne infectious diseases including diarrhea, typhoid, measles,
rubella, kala-azar, malaria and dengue etc. are common in Bangladesh.
Emerging nipah virus and chikungunya are also prevailing in many areas of
the country.
This study was conducted to determine the “Impact of climate change on the
outbreak of infectious diseases among children in Bangladesh: its prevention
and control” in two climate sensitive district of the country. The study area
Rajshahi and Naogaon are the western districts known barindh area in
Bangladesh and poses drought prone plane land, riverine and low lands.
The long-term changes of annual mean, maximum and minimum temperature
of study area over the study period (1964-2011) found to have in general
increasing trends in annual mean and annual mean minimum temperature but
the mean maximum temperature slightly rising in recent past decades.
Seasonal mean temperatures are also found to have increase trend. The
highest average maximum temperature was 30.55
0
C observed in the month
iv
of April in pro monsoon season and the lowest average temperature was
15.45
0
C in the month of January in winter season. The long-term changes in
annual rainfall showed decline trend. The average annual rainfall was 1489
mm/year. Seasonal rainfalls also showed markedly reduced in winter and
post autumn season. Most of the rainfalls occurred in monsoon season that is
also declined in the study area.
The study indicates that the climatic variables including temperature and
rainfall (seasonal and annual) are factors for causing infectious disease
outbreak like diarrhea, kala-azar, measles etc. in the study area. Incidence of
diarrhea shows positive correlation with both annual and seasonal rainfall
and temperature implies that diarrhea as endemic in the study area. Kala-azar
was also found to be positively correlated with rainfall and annual maximum
temperature but found negative with annual minimum temperature.
The primary data reveals that temperature is the main and rainfalls comes
next as causes for diarrhea, kala-azar, measles like disease and newer Nipah
virus infection and their outbreak among children. Data showed that the
children in the study area were highly vaccinated. Among the vaccine
preventable diseases only measles cases and outbreak found. In addition to
laboratory confirmed measles outbreak a large number of measles like
outbreak identified as laboratory confirm rubella outbreak which is newer in
the study area. The incidence of measles like disease was found positive
correlation with maximum temperature and negatively correlated with
average minimum temperature and total annual rainfalls.
To address the existing and future impact of climate change on the outbreak
of infectious diseases among children, climate sensitive infectious disease
surveillance, strengthening of routine immunization and introduction of new
vaccination program need to be considered immediately.
v
Table of Contents
Declaration ....................................... ... ... ... .. ... ... .. ... ... ... .. ... ... ... .. ... ... ..... ... ... .. ... ... .. ... i
Certificate ............................................................................................................. iii
Acknowledgements ................................ ...................... ........................ ................. iv
Abbreviations ....................................................................................................... vi
Abstract ............................................................................................................... vii
List of Contents ..................................................................................................... ix
List of Figure ....................................................................................................... xii
List of Picture .......................................................................................................xv
List of Maps ....................................................................................................... xvi
Chapter One: Introduction... ............................................................................... 1
1.1 The Climate System .............................................................................. 4
1.2 Climate Change and Global Warming ................................................... 5
1.3 Recent Scientific Assessments on Climate Change ................................ 7
1.4 Climate Change in Bangladesh .............................................................. 8
1.4.1 Review of Climate Change in Bangladesh ..............................10
1.4.2 Current Climate in Bangladesh ...............................................13
1.5 Climate and Human Health ...................................................................14
1.5.1 International work program on Climate Change and Health ....16
1.6 Climate Change and Infectious Diseases Outbreak ...............................17
1.6.1 Classification of Infectious Diseases .......................................20
1.6.2 Documented and Predictive Climate/Infectious Disease
Linkages ............................. ............. .............. .............. ...........23
1.6.3 Climate Sensitivities of Infectious Diseases ............................24
1.6.4 Seasonality of Infectious Diseases ..........................................24
1.6.5 Climate Impact on Water Borne Diseases ...............................28
1.6.6 Climate Impact on Vector-borne and Zoonotic Diseases .........29
1.7 Infectious Diseases and its Prevention and Control ...............................30
vi
1.7.1 Water and Food borne Infectious Diseases ..............................31
1.8 Route of Transmission of Water and Food borne Disease .....................33
1.8.1 Air borne Infectious Diseases ..................................................35
1.8.3 Vector-borne Infectious Diseases ............................................39
1.8.3 Emerging and Re-emerging Infectious Disease .......................45
1.9 Background on Climate Change and Health Impacts in Bangladesh .....49
1.10 Objectives of the Study .......................................................................51
1.11 Scope of the Study ..............................................................................52
Chapter Two : Materials and Methods .................................................... 53
2.1 Descriptions of the Study Area .............................................................53
2.2 Secondary Data Collection ...................................................................56
2.3 Primary Data Collection .......................................................................57
Chapter Three : Results ............................................................................ 63
3.1 Climate Characteristics (Temperature and Rainfall) ..............................63
3.2 Climate Sensitive Infectious Disease Profile .........................................68
3.3 Results from Primary Data ...................................................................80
3.3.1 Socio-Demographic Profile of the Study Area ........................81
3.3.2 Common Infectious Diseases in the Study Area .....................83
3.3.3 Respondents’ Opinion on Possible Reasons for Disease
Incidence .................................... ........................... .................84
3.3.4 Incidence of Infectious Diseases over last 10 years ............................86
3.3.5 Respondents’ Knowledge and Understanding on Climate Change .....86
3.3.6 Vaccination Status of Children in the Study Area ..............................87
3.3.7 Incidence of Vaccine Preventable Diseases in Study Area over the
Study Period......................................................................................88
3.3.8 In-depth Investigation of Reported Outbreak in the Study Area .........89
Chapter Four : Discussion ......................................................................... 94
References
......................... ................. ................ ................ ................. ............ 103
Appendices ....................................................................................... 111
vii
List of Tables
Table 1 GCM Estimates of Temperature and Precipitation Changes .................10
Table 2 All Bangladesh Trends in Seasonal and Annual Mean Temperatures ...13
Table 3 Morbidity and mortality due to Nipah or Nipah like Viral
Encepahalitis in Bangladesh during the period from 2001 to 2011 .......48
Table 3.1 Incidence of Some Major Climate Sensitive Disease in Bangladesh ....68
Table 3.2 Values of Correlation coefficient of climatic variables and diarrhoea in
study area during the study period (2000-2011) .....................................74
Table 3.3 Values of Correlation coefficient of climatic variables and Kala
azar in study area during the study period (2000-2011) ........................77
Table 3.4 Values of Correlation coefficient of climatic variables and Measles in
study area during the study period (2000 2011)
.................... ......... .......... .. 80
Table 3.5 Vaccine Preventable Disease in the Study Area ...................................88
Table 3.6 Measles like Outbreak and Cases in the Study Area .............................90
Table 3.7 Vaccination status of Lab Confirm Measles Cases in the Study
Area .............................. ........................... .............................. ..............91
viii
List of Figures
Figure-1.1 Global climate change and health: an old story writ large by A.J.
McMichael) .................................... ............................................ ....... 7
Figure-1.2 Variation in Earth’s average surface temperature, over the past
20000 years ...................................................................................... 8
Figure-1.3 Pathway by which climate change affects human health,
including local modulating influences and the feedback influence
of adaptation measures. .................................................................... 16
Figure 1.4 Presents four main types of Transmission Cycle for Infectious
Diseases. .................................... ........... .............. ............. .............. .. 22
Figure: 1.5 Route of Transmission of Water and Food borne Disease ................ 33
Figure 1.6 Seasonal Incidence of Diarrhea cases in Bangladesh ........................ 34
Figure 1.7 Trend of Measles cases and Vaccination Coverage in Bangladesh ... 37
Figure 1.8 Life-cycle of Kala-azar Parasite ....................................................... 41
Figure-3.1 The annual mean minimum, mean and mean maximum
temperatures in Rajshahi region during the period 1964-2011. ......... 64
Figure-3.2 The annual winter mean, monsoon mean and summer mean
temperatures in Rajshahi region during the period 1964-2011. ......... 64
Figure-3.3 Monthly average maximum and minimum temperatures in
Rajshahi region during the period 1964-2011................................... 65
Figure-3.4 Annual average rainfall in Rajshahi during the year 1964-2011 ....... 66
Figure-3.5 Annual winter and summer rainfall in Rajshahi during the year
1964-2011 ....................................................................................... 67
Figure-3.6 Annual monsoon and post monsoon rainfall in Rajshahi during
the year 1964-2011 .......................................................................... 67
Figure-3.7 Incidence of diarrhoea in Bangladesh during the period of 1999-
2011 ........................................................................................................ 69
ix
Figure-3.8 Incidence of Kala azar in Bangladesh during the period of 1994-
2011 ........................................................................................................ 69
Figure-3.9 Incidence of NIPAH in Bangladesh during the period of 2001-
2011 ................................................................................................ 70
Figure-3.10 Incidence of Measles like cases in Bangladesh during the period
of 1990-2011 ................................................................................... 70
Figure-3.11 Annual incidence of diarrhoea in the study area during the period
of 2000 to 2011 ................................................................................ 72
Figure-3.12 Trends of annual rainfall and diarrhoea incidences in the study
area during the period of 2000 to 2011 ............................................. 72
Figure-3.13 Trend of annual average maximum temperature and diarrhoea
incidences in the study area during the period of 2000 to 2011 ........ 73
Figure-3.14 Trend of annual average minimum temperature and diarrhoea
incidence in Study area during the period of 2000 to 2011 ............... 73
Figure-3.15 Incidence of Kala-azar in study area during the period of 2001 to
2011 ............................................................................................................ 75
Figure-3.16 Seasonal incidence of Kala-azar in study area during the period
of 2001 to 2011 ................................................................................ 75
Figure-3.17 Trend of annual rainfall and Kala-azar incidences in the study are
during the period of 2001 to 2011 .................................................... 76
Figure-3.18 Trend of annual mean maximum temperature and Kala-azar
incidences in the study are during the period of 2001 to 2011 .......... 77
Figure-3.19 Trend of annual mean minimum temperature and Kala-azar
incidences in the study are during the period of 2001 to 2011 .......... 78
Figure-3.20 Incidence of Measles outbreak and cases in study area during the
study period ..................................................................................... 79
Figure-3.21 Seasonal trends of Measles cases in study area during the study
period .......................................................................................................... 79
Figure-3.22 Distribution of household members by sex in study area .................. 81
Figure-3.23 Percent distribution of household member by age group in study area ... 82
Figure-3.24 Percent distribution of respondent mother by education in Study Area .. 83
x
Figure-3.25 Incidences of Infection Diseases among Children in Study Area ...... 84
Figure-3.26 Causes of diarrhoea according to percent respondents ..................... 85
Figure-3.27 Causes of measles according to percent respondents ........................ 86
Figure-3.28 Causes of Kala-azar according to percent respondents ..................... 88
Figure-3.29 Vaccination status (%) of children bellow one year of age in the
study area ........................................................................................ 88
Figure-3.30 Presents the Epidemic Curve of Measles Outbreak in the Study
Area during the study period (2009-2011) ....................................... 91
Figure-3.31 Age distribution of Measles cases in study area ............................... 92
Figure-3.32 Sex Distribution of Measles Cases in the Study Area ....................... 92
Figure-3.33 Comparison of Measles like Outbreak Cases by Lab result in the
study area ........................................................................................ 93
xi
List of Pictures
Picture 1: Disease Transmission through Respiratory Droplets..............................35
Picture 2: Measles like Cases in the Study Area ....................................................38
Picture 3: Complication of Measles like Cases .....................................................39
Picture 4: Picture of Sand Fly ................................................................................42
Picture 5: Breeding place of sand fly .....................................................................43
Picture 6: Resting place of sand fly .......................................................................43
Picture 7: Insecticide Treated Nets with Synthetic Pyrethroid ...............................44
Picture 8: Picture of pteropus Bat .........................................................................46
Picture 9 & 10: Interviewing mother regarding infectious disease and climate
change knowledge in community household and clinic setup ...............58
Picture 11: Interviewing mother about the outbreak of disease ..............................59
Picture 12: Collection of blood sample from patient ..............................................59
Picture 13: Blood sample centrifuge to prepare serum ..........................................60
Picture 14: Cold chain box with centrifuge serum for transportation ....................60
Picture 15: Serum tested for measles and rubella specific IgM .............................61
Picture 16: Interviewing mother regarding vaccination status of the children ........62
xii
List of Maps
Map 1: Map of Bangladesh .................................................................................... 9
Map 2: Map of Rajshahi district ............................................................................54
Map 3: Map of Naogaon district ............................................................................55
Chapter One
General Introduction
Climate is a key determinant of health. The long term good health of population
depends on the continued stability and functioning of the biosphere’s ecological
and physical system. Climate and weather are important components of complex
ecosystems, and with these changes, the dynamic balance between the living
components of ecosystems are often disturbed. Ecosystem instability can result in
changes in pathogen prevalence, altered pathogen transmission profiles, and
increased host susceptibility. These instabilities can have dramatic affects on the
health. Climate constrains the range of infectious diseases, whereas weather affects
the timing and intensity of outbreaks. A long-term warming trend is encouraging
the geographic expansion of several important infections, whereas extreme
weather events are spawning ‘‘clusters’’ of disease outbreaks and a series of
surprises. Ecological changes and economic inequities strongly influence disease
patterns. However, a warming and unstable climate is playing an ever increasing
role in driving the global emergence, resurgence, and redistribution of infectious
diseases (Paul, 2004). All infections involve an agent (or pathogen), host(s), and
the environment. Some pathogens are carried by vectors or require intermediate
hosts to complete their life cycle. Climate can influence pathogens, vectors, host
defenses, and habitat.
Bangladesh is highly vulnerable to natural disasters due to the frequency of extreme
climate events and its high population density. Higher temperatures including more
extreme weather events and sea level rise are already evident in Bangladesh.
Temperature trends for the daily maximum series and the daily minimum series of
2
the annual and seasonal basis have shown that the overall temperature regime in
Bangladesh is showing a rising trend (IPCC 2007). One estimate is that the average
increase in temperature in Bangladesh would be 1.3ºC and 2.6ºC by the year 2030
and 2075 respectively with respect to the base year 1990 (IPCC, 2007). Global
warming will increase the intensity of southwest monsoon, which will, in turn,
increase the water and food born diseases (Earn et. al., 2000). Incidence of vector-
borne diseases like malaria, leishmania and dengue are likely to increase as a result
of climate change in this region. Increase in temperature may provide better
environment for breeding of mosquito and sand fly in places where the temperature
were previously below optimum (Lindsay et al., 1996).
World Health Organization (WHO) demonstrates in a report that more than 33% of
diseases in children under the age of 5 are caused by environmental exposures.
Preventing environmental risk could save as many as four million lives a year in
children alone, mostly in developing countries.
Infectious diseases continue to be the major cause of morbidity and mortality
worldwide. Bangladesh is unfortunately home to many infectious diseases. Over
the last several decades Bangladesh has made remarkable progress in reducing the
human health burden of infectious disease, especially in children, largely due to
reduction in mortality from infectious diseases. Despite substantial progress,
vaccine preventable diseases remain important causes of ill health and premature
death in Bangladesh. In the most recent national demographic and health survey
(year 2011) 62% of deaths among children under the age of 5 years in Bangladesh
were ascribed to infectious diseases. This accounts for 55 deaths per 1000 live
births. To achieve MDGs then childhood infectious disease mortality needs to be
3
reduced by 34 deaths per 1000 live births, or a 38% reduction between 2000 and
2015. Childhood and adult mortality can be reduced dramatically through
improved management of infectious diseases and prevention via introduction of
vaccines and behavior modification. The use of vaccines results in a profound
alteration of the environment in which parasites live. Indeed, the goal of
vaccination is to protect individual hosts and consequently decrease parasite
prevalence. Ultimately, this may even lead to the eradication of the disease (Fine et
al., 1982). These epidemiological consequences of vaccination have received a
considerable amount of attention, both from an empirical and a theoretical
standpoint (Anderson & May 1991; McLean & Blower 1995; Earn et al., 2000;
Rohani et al., 2000; Tildesley et al., 2006). Immunization describes the whole
process of delivery of a vaccine and the immunity it generates in an individual and
population. Government of Bangladesh has adopted a number of national policies
with a view to provide basic health services to all with special emphasis on
children and woman to ensure that they would enjoy their rights. The future of the
nation lies on the head of the children of today. The future will be bright and
prosperous if we provide the opportunities and allow the children to develop their
potentials.
The World Health Organization reports that since 1976, more than 30 diseases
have appeared that are new to medicine, of equal concern is the resurgence and
redistribution of old diseases. There were some researches and studies on climate
change and its impacts in Bangladesh at different times by both government and
non-government organization and institutions. But research on human health
impacts due to climate change in Bangladesh has not gained much focus before
2006. There is very little information about climate change and infectious disease
4
burden in Bangladesh. On 3rd of December 2009 Ministry of Health and Family
Welfare of Bangladesh announced to open a new climate change cell to look into
the climate-induced disease burden in the country.
1.1 The Climate System
Our planet’s climate is always changing. In the past it has altered following natural
causes but at the present the changes have accelerated as a result of human
behavior. During the Earths history, the climate has changed many times and has
included ice ages and period of warmth. Before the Industrial Revolution, natural
factors such as volcanic eruptions, changes in the Earth’s orbit, and the amount of
energy released from the sun were the primary factors affecting the Earth’s climate.
On a global scale, climate is largely regulated by how much energy the Earth
receives from the sun and how much energy it releases back to space. Earth’s
climate is determined by complex interactions between the Sun, oceans,
atmosphere, cryosphere, land surface and biosphere. The Sun is the principal
driving force for weather and climate. Five concentric layers of atmosphere
surround this planet. The lowest layer (troposphere) extends from ground level to
around 10-12 km altitude on average. The weather that affects Earth’s surface
develops within the troposphere. The next major layer (stratosphere) extends to
about 50 km above the surface. The ozone within the stratosphere absorbs most of
the sun’s higher energy ultraviolet rays. Above the stratosphere there are three
more layers: mesosphere, thermosphere and exosphere. Overall, these five layers
of the atmosphere approximately halve the amount of incoming solar radiation that
reaches Earth’s surface. In particular, certain "greenhouse" gases, present at trace
concentrations in the troposphere absorb about 17% of the solar energy passing
5
through it. Of the solar energy that reaches Earth’s surface, much is absorbed and
reradiated as long-wave (infrared) radiation. Some of this outgoing infrared
radiation is absorbed by greenhouse gases in the lower atmosphere, which causes
further warming of Earth’s surface. The greenhouse gases radiate this energy in all
directions, including back to the Earth again. This energy is used in a number of
processes, including heating the ground surface, melting ice and snow, evaporating
water, and plant photosynthesis. Most importantly this energy remains trapped
within the climate system, warming the Earth’s surface to an average of 14°C. This
phenomenon, called the “natural greenhouse effect,” keeps the Earth in a
temperature range that allows life to thrive. Without it, the sun’s heat would escape
and the average temperature of the Earth would drop to –19°C (US Environmental
Protection Agency. Greenhouse effects schematic 2001).
1.2 Climate Change and Global Warming
The terms “global warming” and “climate change” are often used to describe the
same phenomenon. In actuality they are distinguishable as cause and effect, or
problem and consequence. Global warming refers only to the increase in the
temperature of the Earth’s lower atmosphere as a result of the enhanced
greenhouse effect. The resulting impacts of this temperature increase, changes in
many aspects of weather, are referring to as climate change. Thus, we are
experiencing climate change as a result of global warming. Climate change occurs
over decades or longer time-scales. Until now, changes in the global climate have
occurred naturally, across centuries or millennia, because of continental drift,
various astronomical cycles, variations in solar energy output and volcanic activity.
Over the past few decades it has become increasingly apparent that human actions
6
are changing atmospheric composition, thereby causing global climate change
(Albritton and Meiro-Filho, 2001).
Climate change encompasses temperature changes on global, regional, and local
scales, and also changes in the mean and variability of rainfall, winds, and possibly
ocean currents. According to United Nation Framework convention on Climate
Change (UNFCC), climate change is a change of climate which is attributed
directly or indirectly to human activity that alters the composition of the global
atmosphere and which is in addition to natural climate variability observed over
comparable time periods (UNFCC, Geneva). During the twentieth century, world
average surface temperature increased by approximately 0.6 º C and approximately
two-thirds of that warming has occurred since 1975. Climatologists forecast
further warming, along with changes in precipitation and climatic variability,
during the coming century and beyond (Albritton et, al., 2001).
Third Assessment Report (2001), the United Nation’s Intergovernmental Panel on
Climate Change (IPCC) stated: "There is new and stronger evidence that most of
the warming observed over the last 50 years is attributable to human activities and
estimated that the global average temperature will rise by several degrees
centigrade during this century.” Report also projects an increase in average world
surface temperature ranging from 1.4 to 5.8
0
C over the course of twenty first
century (Paul, 2004).
7
1.3 Recent Scientific Assessments on Climate Change
The latest report from the Intergovernmental Panel on Climate Change (IPCC)
makes several compellingly clear points (US Environmental Protection Agency,
2001). First, human-induced warming has apparently begun: the particular pattern
of temperature increase over the past quarter-century has fingerprints that indicate
a substantial contribution from the build-up of greenhouse gases due to human
activities. Second, a coherent pattern of changes in simple physical and biological
systems has become apparent across all continents—the retreat of glaciers, melting
of sea ice, thawing of permafrost, earlier egg-laying by birds, pole wards extension
of insect and plant species, earlier flowering of plants and so on. Third, the
anticipated average surface temperature rise this century, within the range of 1.4 to
5.8° C, would be a faster increase than predicted in the IPCC’s previous major
report, in 1996 (Albritton and Meiro-Filho, 2001). The estimated rise in average
world temperature over the coming century conceals various important details.
(Source: Global climate change and health: an old story writ large by A.J. McMichael)
8
Anticipated surface temperature increases would be greater at higher latitudes,
greater on land than at sea, and would affect the daily minimum night-time
temperatures more than daily maximum temperatures. Global climate change also
would cause rainfall patterns to change with increases over the oceans but a
reduction over much of the land surface.
The long history of climatic fluctuations since the end of the last global glaciation
around 15 000 years ago, along with the evidence of recent temperature rises and
the IPCC’s projected rapid warming in the current century, are summarized in
Figure 1.2.
Source: Global climate change and health: an old story writ large by A.J. McMichael
Figure-1.2 Variation in Earth’s average surface temperature, over the past 20000 years
1.4 Climate Change in Bangladesh
Bangladesh is located between 20
o
to 26
o
North and 88
o
to 92
o
East. It is bordered
on the west, north and east by India, on the south-east by Myanmar, and on the
south by the Bay of Bengal (Map 1). Most of the country is low-lying land
9
comprising mainly the delta of the Ganges and Brahmaputra rivers. Floodplains
occupy 80% of the country. Mean elevations range from less than 1 meter on tidal
floodplains, 1 to 3 meters on the main river and estuarine floodplains, and up to 6
meters in the Sylhet basin in the north-east (Rashid, 1991, Ahmed and Mirza,
2000). Only in the extreme northwest are elevations greater than 30 meters above
the mean sea level. The northeast and southeast portions of the country are hilly,
with some tertiary hills over 1000 meters above mean sea level (Huq and
Asaduzzaman, 1999).
Map1. Map of Bangladesh
10
Bangladesh ranks low on just about all measures of economic development. This
low level of development, combined with other factors such as its geography and
climate, makes the country quite vulnerable to climate change. With a population
of over 14,97,72,364 people in a small area and a population density of more than
1,209 persons per km, and 71.90% of the population lives in rural areas,
Bangladesh is a very densely populated country (World Bank). Higher population
density increases vulnerability to climate change because more people are exposed
to risk and opportunities for migration within a country are limited.
1.4.1 Review of Climate Change in Bangladesh
The Bangladesh Country Study for the U.S. Country Studies Program used an
older version of the Geophysical Fluid Dynamics Laboratory (GFDL) transient
model (Manabe et al., 1991) and projected that temperature would rise 1.3°C by
2030 (over mid-20th century levels) and 2.6°C by 2070. The report estimated that
winter warming would be greater than summer warming. The study also estimated
little change in winter precipitation and an increase in precipitation during the
monsoon (Ahmed and Alam, 1998, Ahmed, 2004). The results of the
MAGICC/SCENGEN analysis for Bangladesh are shown in Table 1.
Table1. GCM Estimates of Temperature and Precipitation Changes
11
The climate models all estimate a steady increase in temperatures for Bangladesh,
with little inter-model variance somewhat more warming is estimated for winter
than for summer (Ahmed and Alam, 1998, Ahmed, 1986). With regard to
precipitation - whether there is an increase or decrease under climate change is a
critical factor in estimating how climate change will affect Bangladesh, given the
country’s extreme vulnerability to water related disasters. The key is what happens
during the monsoon. More than 80% of the 2,300 mm of annual precipitation that
falls on Bangladesh comes during the monsoon period (Smith et al., 1998). Most
of the climate models estimate that precipitation will increase during the summer
monsoon because they estimate that air over land will warm more than air over
oceans in the summer. This will deepen the low pressure system over land that
happens anyway in the summer and will enhance the monsoon (Ahmed, 2000). It
is notable that the estimated increase in summer precipitation appears to be
significant; it is larger than the standard deviation across models. This does not
mean that increased monsoon is certain, but increases confidence that it is likely to
happen. The climate models also tend to show small decreases in the winter
months of December through February. The increase is not statistically significant,
and winter precipitation is just over 1% of annual precipitation. However, with
higher temperatures increasing evapotranspiration combined with a small decrease
in precipitation, dry winter conditions, even drought, are likely to be made worse.
First major work on local level change of temperature and rainfall elements of
climate has been undertaken by Climate Change Cell (CCC 2009). They used a
model called PRECIS (Providing Regional Climates for Impact Studies),
developed by Hadley Center, UK. The model used data from 31 weather stations
of Bangladesh and the major findings of PRECIS model are,
12
• Rainfall during monsoon and post-monsoon periods will increase where it
will remain close to historical amount during dry season.
• Rainfall during pre-monsoon will fluctuate in different years.
• Over the country, rainfall will increase 4%, 2.3%, 6.7%, in 2030, 2050,
2070 respectively in reference to the observed baseline period.
• Monthly average maximum temperature will change from -1.2 to 4.7
degrees centigrade in 2030; from -1.2 to 2.5
0
C in 2050 and from -1.2 to 3
0
C in 2070.
• Maximum temperature will increase during monsoon period and it will
decrease in other periods.
• Monthly average minimum temperature will increase in all periods and vary
from 0.3 to 2.4
0
C in 2030, from 0.2 to 2.3
0
C in 2050 and from -0.6 to 3.3
0
C in 2070.
• Variation of rainfall and temperature (both maximum and minimum) in any
location over Bangladesh and in a particular month is quite large than the
seasonal and annual average.
• Maximum temperature will increase about 5.97
0
C in Bogra in 2030.
Second major work was also conducted by CCC (2008), where the attempted to
characterize changes of Bangladesh climate. They also considered March, April
and May as summer and November, December, January and February as winter
season. The research showed that the annual and seasonal mean temperatures are
found to have in general increasing trends in Bangladesh. The overall trend in
mean annual temperature is found to be +0.10 and +0.21
0
C per decade for years
1948-2007 and 1980 to 2007 respectively. It concludes that warming has been
more rapid in recent decades. In addition Rahman et al., 1997 found evidence of
changes in monsoon rainfall pattern.
13
Table 2: All Bangladesh Trends in Seasonal and Annual Mean Temperatures
Season
Trend in all Bangladesh mean temperatures (
0
C
per century) for data period of
1948-2007 1980-2007
Winter (Nov-Feb) +1.67 +1.33
Summer (Mar-May) +0.26 +2.25
Monsoon (Jan-Oct) +1.05 +2.44
Annual (Jan-Dec) +1.03 +2.14
Source: Climate Change Cell (CCC) 2008
1.4.2 Current Climate in Bangladesh
Bangladesh has a humid, warm, tropical climate. Its climate is influenced primarily
by monsoon and partly by pre-monsoon and post-monsoon circulations. The south-
west monsoon originates over the Indian Ocean and carries warm, moist, and
unstable air. The monsoon has its onset during the first week of June and ends in
the first week of October, with some inter-annual variability in dates. Besides
monsoon, the easterly trade winds are also active, providing warm and relatively
drier circulation.
In Bangladesh there are four prominent seasons, namely, winter (December to
February), Pre-monsoon (March to May), Monsoon (June to early-October), Post-
monsoon (late-October to November). The general characteristics of the seasons
are as follows:
• Winter (December to February) is relatively cooler and drier, with the average
temperature ranging from a minimum of 7.2 to 12.8°C to a maximum of 23.9
to 31.1°C. The minimum occasionally falls below 5
0
C in the north though
frost is extremely rare. There is a south to north thermal gradient in winter
mean temperature: generally the southern districts are 5
0
C warmer than the
northern districts.
• Pre-monsoon (March to May) is hot with an average maximum of 36.7°C,
predominantly in the west for up to 10 days, very high rate of evaporation, and
14
erratic but occasional heavy rainfall from March to June. In some places the
temperature occasionally rises up to 40.6°C or more. The peak of the maximum
temperatures are observed in April, the beginning of pre-monsoon season. In
pre monsoon season the mean temperature gradient is oriented in southwest to
northeast direction with the warmer zone in the southwest and the cooler zone
in the northeast.
• Monsoon (June to early-October) is both hot and humid, brings heavy torrential
rainfall throughout the season. About four-fifths of the mean annual rainfall
occurring during monsoon. The mean monsoon temperatures are higher in the
western districts compared to that for the eastern districts. Warm conditions
generally prevail throughout the season, although cooler days are also observed
during and following heavy downpours.
• Post-monsoon (late-October to November) is a short-living season
characterized by withdrawal of rainfall and gradual lowering of night-time
minimum temperature.
The mean annual rainfall is about 2300mm, but there exists a wide spatial and
temporal distribution. Annual rainfall ranges from 1200mm in the extreme west to
over 5000mm in the east and north-east (MPO, 1991).
1.5 Climate and Human Health
Global average temperatures are projected to increases, and it is known that
climate change in the next hundred years will be significant and by the year 2100
best estimates predict between a 1.8˚ C and 4˚ C rise in average global temperature,
although it could possibly be as high as 6.4˚ C. (James, august 2008) Evidence is
mounting that changes in the broad-scale climate system may already be affecting
human health, including mortality and morbidity from extreme heat, cold, drought
or storms; changes in air and water quality; and changes in the ecology of
15
infectious diseases (Patz, et al.,1996). All over the world, climate change related
impacts including prolong flood, heat wave, drought, sea level rise, salinity,
temperature and rainfall variations have become very evident (UNDP human
development report 2007). People are directly exposed to changing weather
patterns (temperature, precipitation, sea-level rise and more frequent extreme
events) and indirectly through changes in the quality of water, air and food. These
direct and indirect exposures can cause death, disability and suffering
(Rahman, 2008), (Shahid, 2009). WHO has estimated that, globally, over 150000
deaths annually result from recent change in the world’s climate relative to the
baseline average climate of 1961–1990 (McMicchael, et al., 2006). Fourth
Assessment Report (AR4) of the Intergovernmental Panel on Climate Change
(IPCC) states clearly that climate change is contributing to the global burden of
disease and premature deaths (Rahman, 2008).
Climate change also brings new challenges to the control of infectious diseases.
Many of the major killers are highly climate sensitive as regards temperature,
humidity and rainfall, including air born (measles) and the water born (diarrhoeal)
diseases, as well as diseases including malaria, kala azar, dengue and other
infections carried by vectors.
Global climate change would affect human health via pathways of varying
complexity, scale and directness and with different timing. Similarly, impacts
would vary geographically as a function both of environment and topography and
of the vulnerability of the local population. Impacts would be both positive and
negative (although expert scientific reviews anticipate predominantly negative).
16
Fig-1.3
The main pathways and categories of health impact of climate change are
shown in
Figure 1.3 Pathway by which climate change affects human health, including local
modulating influences and the feedback influence of adaptation measures.
(Source: Global climate change and health: an old story writ large by A.J. McMichael)
The effects on human health can be divided into two categories; direct effect on
the illness such as heat-shock and on increased mortality in population with other
diseases and there is an indirect effect of climate change on health. The major
indirect effect is on infectious diseases. Among infectious diseases, vector-born,
water-born and air-born infectious diseases are main categories.
1.5.1 International work program on Climate Change and Health
In May 2008, the World Health Assembly (which comprises the 193 Member
States of the World Health Organization) passed Resolution No. 61.39 calling on
WHO to take systematic action on the global health issue. The resolution called on
WHO: “to continue close cooperation with appropriate UN agencies, other
agencies and funding bodies, and Member States, to develop capacity to assess the
risk from Climate Change (CC) for human health and to implement effective
response measures, by promoting further research and projects in this area”.
17
Based on WHO partial estimate of climate change health impacts in the year 2000
(McMichael et al., 2004), an estimated 200,0000 deaths currently occur each year
in the world’s low-income countries from a subject of climate sensitive health
outcomes. Around 85% of those deaths are in children. Preventing environmental
risk could save as many as four million lives a year in children alone, mostly in
developing countries. According to a 2003 report authored by WHO, the UNEP
and the WMO, climate change is responsible for 2.4 per cent of all cases of
diarrhea worldwide and for two per cent of all cases of malaria. Moreover, in the
year 2000 an estimated 150,000 deaths were caused by climate change.
1.6 Climate Change and Infectious Diseases Outbreak
The combination of higher temperatures and potential increases in summer
precipitation could create the conditions for greater intensity or spread of many
infectious diseases. The causes of outbreaks of infectious disease are quite
complex and often do not have a simple relationship with increasing temperature
or change in precipitation. It is not clear if the magnitude of the change in health
risks resulting from climate change will be significant compared to current risks.
Global warming will increase the intensity of southwest monsoon, which will, in
turn, bring catastrophic ravages like floods and have reaching consequences on
health. During and after floods, the water-borne diseases increases due to
contamination of surface water. Incidence of vector-borne diseases like malaria,
leishmania, dengue are likely to increase as a result of climate change in this
region specially in Bangladesh. Increase in temperature may provide better
environment for breeding of mosquito and sand fly in places where the
temperature were previously bellow optimum. This may increase the human
contact with the vectors responsible for spread of diseases. On the whole climate
change is expected to present increased risks to human health in Bangladesh,
especially in light of the poor state of the country’s public health infrastructure.
18
Early identification of an infectious disease outbreak is an important first step
towards implementation of effective disease interventions and reducing resulting
mortality and morbidity in human populations. Outbreak is occurring in every
corner of the world. Some are emerging (e.g. Nipah) and some are reemerging (e.g.
Influenza). Some outbreaks make global attention (e.g. H1N1, Nipah etc) some are
of regional concern or country specific (e.g. Diarrhoea, Kala azar etc.). In the
majority of the of cases epidemics of infectious disease are generally well under way
before authorities are notified and able to control the epidemic or mitigate the effects.
An infectious disease is a clinically evident illness resulting from the presence of
pathogenic microbial agents, including pathogenic viruses, pathogenic bacteria,
fungi, protozoa and multicellular parasites.
All infections involve an agent (or pathogen), host(s), and the environment. Some
pathogens are carried by vectors or require intermediate hosts to complete their life
cycle. Climate can influence pathogens, vectors, host defenses, and habitat.
A range of infectious (particularly vector-born) diseases are geographically and
temporally limited by environmental variables such as climate and vegetation
patterns. Climate factor’s impact on infectious diseases can be divided into three
main effects: on human behavior, on the disease pathogen; on the disease vector,
where relevant:
Human Behavior
Climate variability directly influences human behavior, which in turn can
determine disease transmission patterns. The strong seasonal pattern of influenza
infection in Europe, for example, is thought to reflect human’s increase tendency
to spend more time indoors during winter months (Halstead, 1996). Also the peak
of gastro-enteritis in temperate developed countries during summer months can be
19
related to changes in human behavior (e.g. more picnics) associated with warmer
temperatures (Altekruse et al. 1998).
Disease Pathogens
For infectious diseases where the pathogen replicates outside the final host (i.e. in
the environment or an intermediate host or vector), climate factors can have a
direct impact on the development of the pathogen. Most viruses, bacteria and
parasites do not replicate bellow a certain temperature threshold (e.g. 18
0
C for the
malaria parasite Plasmodium falciparum and 20
0
C for the Japanese encephalitis
virus; Macdonald, 1957, Mellor and Leake, 2000). Ambient temperature increases
above this threshold will shorten the development time of the pathogen.
Disease Vectors
The geographical distribution and development rate of insect vectors is strongly
related to temperature, rainfall and humidity. A rise in temperature accelerate the
insect metabolic rate, increase egg production and makes blood feeding more
frequent (e.g. Mellor and Leake 2000). The influence of rainfall is also significant.
Rainfall has an indirect effect on vector longevity through its effect on humidity.
Relatively wet conditions may create favorable insect habitats, thereby increasing
the geographical distribution and seasonal abundance of disease vectors. In other
cases excess rainfall may have catastrophic effects on local vector populations if
flooding washes away breeding sites. Even where linkage between disease and
climate are relatively strong, other non-climatic factors also may have a significant
impact on the timing and severity of disease outbreaks. One such factor is
population vulnerability (e.g. influenced by herd immunity and malnutrition). In
Kenya, for example, Shanks et al., (2000) have argued that malaria epidemics in
the western highlands may occur only when the non - immune population of the
population has grown by recovery, births and immigration because local children
20
surviving to adulthood develop immunity. Human-related factors such as
population movements and agricultural practices also can have considerable
impact on disease patterns at various scales. For example, the prevalence of
malaria and leishmaniasis sometimes is strongly related to irrigation schemes and
deforestation (e.g. Campbell-Lendrum et al., 2001, Guthmann et al., 2002)
1.6.1 Classification of Infectious Diseases
Broadly, infectious diseases may be classified into two categories based on the
mode of transmission: those spread directly from person to person (through direct
contact or droplet exposure) and those spread indirectly through an intervening
vector organism (mosquito or tick) or a non-biological physical vehicle (soil or
water). Infectious diseases also may be classified by their natural reservoir as
anthroponoses (human reservoir) or zoonoses (animal reservoir).
Disease Classifications Relevant to Climate/Health Relationships
Several different schemes allow specialists to classify infectious diseases. For
clinicians who are concerned with treatment of infected patients, the clinical
manifestation of the disease is of primary importance. Alternatively,
microbiologists tend to classify infectious diseases by the defining characteristics
of the microorganisms, such as viral or bacterial. For epidemiologists the two
characteristics of foremost importance are the method of transmission of the
pathogen and its natural reservoir, since they are concerned primarily with
controlling the spread of disease and preventing future outbreaks (Nelson, et. al.).
Climate variability’s effect on infectious diseases is determined largely by the
unique transmission cycle of each pathogen. Transmission cycles that require a
vector or non-human host are more susceptible to external environmental
influences than those diseases which include only the pathogen and human.
21
Important environmental factors include temperature, precipitation and humidity.
Several possible transmission components include pathogen (viral, bacterial, etc.),
vector (mosquito, sand fly, snail, etc.), non-biological physical vehicle (water, air,
soil, etc.), non-human reservoir (mice, deer, etc.) and human host. Epidemiologists
classify infectious diseases broadly as anthroponoses or zoonoses, depending on
the natural reservoir of the pathogen; and direct or indirect, depending on the mode
of transmission of the pathogen. Figure 6.1 illustrates these four main types of
transmission cycles for infectious diseases. The following is a description of each
category of disease, discussed in order of probable increasing susceptibility to
climatic factors (Wilson, 2001).
Directly Transmitted Diseases
Anthroponoses
Directly transmitted anthroponoses include diseases in which the pathogen
normally is transmitted directly between two human hosts through physical contact
or droplet exposure. The transmission cycle of these diseases comprises two
elements: pathogen and human host. Generally, these diseases are least likely to be
influenced by climatic factors since the agent spends little to no time outside the
human host. These diseases are susceptible to changes in human behavior, such as
crowding and inadequate sanitation that may result from altered land-use caused
by climatic changes. Examples of directly transmitted anthroponoses include
measles, Rubella, Tuberculosis (Wilson, 2001).
22
Figure 1.4: Presents four main types of Transmission Cycle for Infectious Diseases.
Indirectly Transmitted Diseases (Anthroponoses & Zoonoses)
Indirectly transmitted anthroponoses are a class of diseases defined by pathogen
transmission between two human hosts by either a physical vehicle (soil) or a
biological vector (tick). These diseases require three components for a complete
transmission cycle: the pathogen, the physical vehicle or biological vector, and the
human host. Most vectors require a blood meal from the vertebrate host in order to
sustain life and reproduce. Indirectly transmitted anthroponoses include
leshmaniasis, malaria and dengue fever, whereby the respective leishmania
parasite, malaria parasite and the dengue virus are transmitted between human
hosts by mosquito vectors (vector-borne disease). Indirectly transmitted water-
borne anthroponoses are susceptible to climatic factors because the pathogens exist
in the external environment during part of their life cycles. Flooding may result in
the contamination of water supplies or the reproduction rate of the pathogen may
be influenced by ambient air temperatures (Wilson, 2001). Cholera is an indirectly
transmitted water-borne anthroponose that is transmitted by a water vehicle: the
bacteria (Vibrio cholerae) reside in marine ecosystems by attaching to
zooplankton. Survival of these small crustaceans in turn depends on the abundance
of their food supply, phytoplankton. Phytoplankton populations tend to increase
23
(bloom) when ocean temperatures are warm. As a result of these ecological
relationships, cholera outbreaks occur when ocean surface temperatures rise
(Colwell, 1996). Indirectly transmitted zoonoses are similar to indirectly
transmitted anthroponoses except that the natural cycle of transmission occurs
between nonhuman vertebrates: humans are infected due to accidental encounters
with an infected vehicle or vector.
1.6.2 Documented and Predictive Climate/Infectious Disease Linkages
The seasonal patterns and climatic sensitivities of many infectious diseases are
well known; the important contemporary concern is the extent to which changes in
disease patterns will occur under the conditions of global climate change. Over the
past decade or so this question has stimulated research into three concentrations.
First, can the recent past reveal more about how climatic variations or trends affect
the occurrence of infectious diseases?
Second, is there any evidence that infectious diseases have changed their prevalence
in ways that are reasonably attributable to climate change?
Third, can existing knowledge and theory be used to construct predictive models
capable of estimating how future scenarios of different climatic conditions will
affect the transmissibility of particular infectious diseases?
Modifying Influences on Infectious Disease
Climate is one of several important factors influencing the incidence of infectious
diseases. Other important considerations include socio demographic influences
such as human migration and transportation; and drug resistance and nutrition; as
well as environmental influences such as deforestation; agricultural development;
water projects; and urbanization. In this era of global development and land-use
24
changes, it is highly unlikely that climatic changes exert an isolated effect on
disease; rather the effect is likely dependent on the extent to which humans cope
with or counter the trends of other disease modifying influences.
1.6.3 Climate Sensitivities of Infectious Diseases
Both the infectious agent (protozoa, bacteria, viruses, etc) and the associated
vector organism (mosquitoes, ticks, sand flies, etc.) are very small and devoid of
thermostatic mechanisms. Their temperature and fluid levels are therefore
determined directly by the local climate. Hence, there is a limited range of climatic
conditions—the climate envelope—within which each infective or vector species
can survive and reproduce. It is particularly notable that the incubation time of a
vector-borne infective agent within its vector organism is typically very sensitive
to changes in temperature, usually displaying an exponential relationship. Other
climatic sensitivities for the agent, vector and host include level of precipitation,
sea level elevation, wind and duration of sunlight.
1.6.4 Seasonality of Infectious Diseases
Seasonal change in the incidence of infectious diseases is a common phenomenon
in both temperate and tropical climates. However, the mechanisms responsible for
seasonal disease incidence, and the epidemiological consequences of seasonality,
are poorly understood with rare exception. Seasonal infections of humans range
from childhood diseases, such as measles, diphtheria and chickenpox, to faecal–
oral infections, such as cholera and rotavirus, vector-borne diseases including
malaria and even sexually transmitted gonorrhoea (Gubler, 2001).
Patterns of winter mortality and infectious disease using the example of cyclic
influenza and acute respiratory illness outbreaks occurring in the late fall, winter and
early spring in North America. This disease pattern may result from increased
25
likelihood of transmission due to indirect social or behavioral adaptations to the cold
weather such as crowding indoors. Another possibility is that it may be attributed
directly to pathogen sensitivities to climatic factors such as humidity. In addition to
influenza, several other infectious diseases exhibit cyclic seasonal patterns, which
may be explained by climate. In diverse regions around the world, enteric diseases
show evidence of significant seasonal fluctuations. In Scotland, campylobacter
infections are characterized by short peaks in the spring (Colwell & Patz, 1998). In
Bangladesh, diarrheal disease (cholera) outbreaks occur during the monsoon season
(Colwell, 1996). In Peru, cyclospora infections peak in the summer and subside in
the winter (Madico, et al., 1997). Similarly, some vector-borne diseases (e.g.
malaria, kalaazar and dengue fever) also show significant seasonal patterns whereby
transmission is highest in the months of heavy rainfall and humidity. Epidemics of
other infections (e.g. meningococcal meningitis) tend to erupt during the hot and dry
season and subside soon after the beginning of the rainy season in sub- Saharan
Africa (Moore, 1992). Seasonal fluctuations of infectious disease occurrence imply
an association with climatic factors. However, to prove a causal link to climate, non-
climatic factors must be considered. Furthermore, in order to assess long-term
climate influences on disease trends, data must span numerous seasons and utilize
proper statistics to account for seasonal fluctuations.
Vector-borne Diseases
Important properties in the transmission of vector-borne diseases include:
Vectors, pathogens, and hosts each survive and reproduce within certain optimal
climatic conditions and changes in these conditions can modify greatly these
properties of disease transmission. The most influential climatic factors for vector
borne diseases include temperature and precipitation but sea level elevation, wind,
and daylight duration are additional important considerations.
26
Temperature Sensitivity
Extreme temperatures often are lethal to the survival of disease-causing pathogens
but incremental changes in temperature may exert varying effects.
Where a vector lives in an environment where the mean temperature approaches
the limit of physiological tolerance for the pathogen, a small increase in
temperature may be lethal to the pathogen. Alternatively, where a vector lives in
an environment of low mean temperature, a small increase in temperature may
result in increased development, incubation and replication of the pathogen
(Lindsay & Birley, 1996, Bradley, 1993). Temperature may modify the growth of
disease carrying vectors by altering their biting rates, as well as affect vector
population dynamics and alter the rate at which they come into contact with
humans. Finally, a shift in temperature regime can alter the length of the
transmission season (Gubler, et al., 2001). Disease carrying vectors may adapt to
changes in temperature by changing geographical distribution. An emergence of
malaria in the cooler climates of the African highlands may be a result of the
mosquito vector shifting habitats to cope with increased ambient air temperatures
(Cox, et al., 1999).
Precipitation Sensitivity
Variability in precipitation may have direct consequences on infectious disease
outbreaks. Increased precipitation may increase the presence of disease vectors by
expanding the size of existent larval habitat and creating new breeding grounds. In
addition, increased precipitation may support a growth in food supplies which in
turn support a greater population of vertebrate reservoirs. Unseasonable heavy
rainfalls may cause flooding and decrease vector populations by eliminating larval
habitats and creating unsuitable environments for vertebrate reservoirs.
Alternatively, flooding may force insect or rodent vectors to seek refuge in houses
27
and increase the likelihood of vector-human contact. Vector-borne pathogens
spend part of their life-cycle in cold-blooded arthropods that are subject to many
environmental factors. Changes in weather and climate that can affect transmission
of vector borne diseases include temperature, rainfall, wind, extreme flooding or
drought, and sea level rise.
Temperature Effects on Selected Vectors and Vector-borne Pathogens
Vector
• Survival can decrease or increase depending on species;
• Some vectors have higher survival at higher latitudes and altitudes with higher
temperatures;
• Changes in the susceptibility of vectors to some pathogens e.g. higher
temperatures reduce size of some vectors but reduce activity of others;
• Changes in the rate of vector population growth;
• Changes in feeding rate and host contact (may alter survival rate);
• Changes in seasonality of populations.
Pathogen
• Decreased extrinsic incubation period of pathogen in vector at higher temperatures
• Changes in transmission season
• Changes in distribution
• Decreased viral replication.
Effects of Changes in Precipitation on Selected Vector-borne Pathogens
Vector
• Increased rain may increase larval habitat and vector population size by
creating new habitat
• Excess rain or snowpack can eliminate habitat by flooding, decreasing vector
population
28
• Low rainfall can create habitat by causing rivers to dry into pools (dry season
malaria)
• Decreased rain can increase container-breeding mosquitoes by forcing
increased water storage
• Epic rainfall events can synchronize vector host-seeking and virus transmission
• Increased humidity increases vector survival; decreased humidity decreases
vector survival.
Pathogen
Few direct effects but some data on humidity effects on malarial parasite
development in the anopheline mosquito host.
Vertebrate host
• Increased rain can increase vegetation, food availability, and population size
• Increased rain can cause flooding: decreases population size but increases
human contact.
1.6.5 Climate Impact on Water Borne Diseases
Climate directly impacts the incidence of waterborne disease through effects on
water temperature and precipitation frequency and intensity. These effects are
pathogen and pollutant specific, and risks for human disease are markedly affected
by local conditions, including regional water and sewage treatment capacities and
practices. Domestic water treatment plants may be susceptible to climate change
leading to human health risks. For example, droughts may cause problems with
increased concentrations of effluent pathogens and overwhelm water treatment
plants; aging water treatment plants are particularly at risk. Urbanization of coastal
regions may lead to additional nutrient, chemical, and pathogen loading in runoff.
Our understanding of weather and climate impacts on specific pathogens is
incomplete. Climate also indirectly impacts waterborne disease through changes in
29
ocean and coastal ecosystems including changes in pH, nutrient and contaminant
runoff, salinity, and water security. These indirect impacts are likely to result in
degradation of fresh water available for drinking, washing food, cooking, and
irrigation, particularly in developing and emerging economies where much of the
population still uses untreated surface water from rivers, streams, and other open
sources for these needs. Even in countries that treat water, climate-induced
changes in the frequency and intensity of extreme weather events could lead to
damage or flooding of water and sewage treatment facilities, increasing the risk of
waterborne diseases. Severe outbreaks of cholera, in particular, have been directly
associated with flooding in Africa and India. A rise in sea level, combined with
increasingly severe weather events, is likely to make flooding events
commonplace worldwide. Ecosystem degradation from climate change will likely
result in pressure on agricultural productivity, crop failure, malnutrition,
starvation, increasing population displacement, and resource conflict, all of which
are predisposing factors for increased human susceptibility and increased risk of
waterborne disease transmission due to surface water contamination with human
waste and increased contact with such waters through washing and consumption.
Both naturally occurring and pollution-related ocean health threats will likely be
exacerbated by climate change. Other climate-related environmental changes may
impact marine food webs as well, such as pesticide runoff, leaching of arsenic,
fluoride, and nitrates from fertilizers, and lead contamination of drinking and
recreational waters through excess rainfall and flooding.
1.6.6 Climate Impact on Vector-borne and Zoonotic Diseases
Vector-borne and Zoonotic Disease (VBZD) ecology is complex, and weather and
climate are among several factors that influence transmission cycles and human
disease incidence. Changes in temperature and precipitation patterns affect VBZD
30
directly through pathogen host-vector interactions, and indirectly through
ecosystem changes (humidity, soil moisture, water temperature, salinity, acidity)
and species composition.
Social and cultural behaviors also affect disease transmission. Many VBZD exhibit
some degree of climate sensitivity, and ecological shifts associated with climate
variability and long-term climate change are expected to impact the distribution
and incidence of many of these diseases. Similarly, certain VBZD may decrease in
particular regions as habitats become less suitable for host or vector populations
and for sustained disease transmission.
1.7 Infectious Diseases and its Prevention and Control
Climate is one of several factors that can influence the spread of infectious disease.
Human activities and behaviors also are critical determinants of disease
transmission. Climate change is likely to increase the incidence of water-borne,
vector-borne and air-borne infectious diseases. Temperature, precipitation and
humidity influence the spread of these diseases. Bacteria, parasites, and their
vectors may breed faster and live longer in warmer, wetter conditions in
Bangladesh. Though biological and technical knowledge are needed to prevention
and control the spread of infectious diseases, additional requirements include
political will, financial resources and national stability.
The major infectious diseases of Bangladesh are:
1. Viral: Measles, Rubella, Hepatitis A, Hepatitis B, Influenza, Polio, Dengue,
Japanese encephalitis, NIPAH, Chikungunia etc.
2. Bacterial: Diarrhoeal disease, Tuberculosis, Tetanus, Pertusis, Meningitis,
Diphtheria, Typhoid fever etc.
3. Protozoal: Malaria, Kala azar etc.
31
1.7.1 Water and Food borne Infectious Diseases
Climate change could cause an increase in the incidence of water- and food borne
illnesses in a number of ways. Most of the viruses, bacteria and protozoa that
cause water and food borne diseases thrive in warm water and weather. Therefore,
increased water and air temperatures could stimulate the growth of harmful
pathogens. In addition, increased rainfall events can lead to these pathogens
being deposited in water, thereby leading to contamination. According to a study
published in the American Journal of Health, for 68 per cent of all waterborne
disease outbreaks in the United States between 1948 and 1994, there was a
significant association with preceding heavy rainfall events. Water can also
become contaminated through surface runoff during a heavy rainfall, which can
allow pathogens to find their way into aquifers, wells and drinking water.
Drought can also play a role in water contamination. During a drought period
there is less runoff flowing into lakes, ponds and streams. This can lead to low
water levels, which means that less water is available to disperse and dilute
pollutants. Low water levels also mean higher temperature water and increases in
the potential for algae growth. Food poisoning is associated with warm weather.
During warmer weather people more frequently eat outdoors and may leave
foods in the sun without proper refrigeration. Higher temperatures favour the
multiplication of harmful bacteria, such as Salmonella. For this reason, a
seasonal pattern is often observed, with a peak in cases of food poisoning during
the summer months. More than 100 types of pathogenic bacteria, viruses and
protozoa can be found in contaminated water, many of which have been
implicated in a variety of water and food borne illnesses. Diarrhoea is the
common water and food borne disease worldwide.
32
Diarrhoeal Disease
Diarrhoea is caused by infectious organisms, including viruses, bacteria, protozoa,
and helminthes that are transmitted from the stool of one individual to the mouth
of another termed the fecal-oral transmission. Diarrhoea is a leading cause of
illness and death among children in developing countries, where an estimated 1.3
thousand million episodes and 4 million deaths occur each year in under-fives.
Worldwide, these children experience an average of 3.3 episodes each year, but in
some areas the average exceeds nine episodes each year. Where episodes are
frequent, young children may spend more than 15% of their days with diarrhea.
About 80% of deaths due to diarrhoea occur in the first two years of life. The main
cause of death from acute diarrhoea is dehydration, which results from the loss of
fluid and electrolytes in diarrhoeal stools.
Diarrhoea is usually defined in epidemiological studies as the passage of three or
more loose or watery stools in a 24-hour period, a loose stool being one that would
take the shape of a container. However, mothers may use a variety of terms to
describe diarrhoea, depending, for example, upon whether the stool is loose, watery,
bloody or mucoid, or there is vomiting. The most important causes of acute watery
diarrhoea in young children in developing countries are rotavirus, enterotoxigenic
Escherichia coli, Shigella, Campylobacter jejuni, and cryptosporidia. In some areas,
Vibrio cholerae 01, Salmonella and enteropathogenic E. coli are also important
causes.
Routes of Transmission
The infectious agents that cause diarrhoea are usually spread by the faecal-oral
route, which includes the ingestion of faecally contaminated water or food, person-
33
to-person transmission, and direct contact with infected faeces. Human faces are
the primary source of diarrhoeal pathogens although the animal faces too contain
the micro-organisms that can cause diarrhea.
Figure: 1.5 Route of Transmission of Water and Food borne Disease
Seasonality
Distinct seasonal patterns of diarrhoea occur in many geographical areas. In
temperate climates, bacterial diarrhoea tend to occur more frequently during the
warm season, whereas viral diarrhoea, particularly disease caused by rotavirus,
peak during the winter. In tropical areas, rotavirus diarrhoea tends to occur
throughout the year, increasing in frequency during the drier, cool months,
whereas bacterial diarrhoea tend to peak during the warmer, rainy season.
)DHF HV
)OLHV +DQGV
:DWH U
0RXWK
)RRG
34
Figure 1.6 showing the seasonal incidence of diarrhea cases in Bangladesh
year 1998-2009.
0
1000000
2000000
3000000
4000000
5000000
6000000
7000000
8000000
Winter Summer Monsoon Autumn
Prevention and Control of Diarrhoea
Although a wide variety of infectious agents cause diarrhoea, they are all
transmitted by common faecal-oral pathways, such as contaminated water, food,
and hands. Measures taken to interrupt the transmission of the causative agents
should focus on these pathways. Important measures of proven efficacy include:
•
Giving only breast milk for the first 4-6 months of life;
•
Avoiding the use of infant feeding bottles;
•
Improving practices related to the preparation and storage of weaning foods
(to minimize microbial contamination and growth);
•
Using clean water for drinking;
•
Washing hands (after defecation or handling faeces, and before preparing
food or eating); and
•
Safely disposing of faeces, including infant faeces.
•
Immunizing against measles and rota virus.
35
1.8.1 Air borne Infectious Diseases
Pathogens of air borne infectious diseases are normally transmitted directly
between two human hosts through physical contact or droplet exposure. The
transmission cycle of these diseases comprises two elements: pathogen and human
host. Generally, these diseases are least likely to be influenced by climatic factors
since the agent spends little to no time outside the human host. These diseases are
susceptible to changes in human behavior, such as crowding, schooling, socio-
cultural gathering and inadequate sanitation that may result from altered land-use
caused by climatic changes.
Picture 1: Disease Transmission through Respiratory Droplets
Directly transmitted air borne infectious diseases include measles, rubella, mumps,
and tuberculosis (Wilson, 2001).
Measles
Measles is the most contagious disease known to man. It is a major childhood
killer in developing countries - accounting for about 900 000 deaths a year. The
mean age of infection is about 9-12 months but varies among countries in large
part due to differences in passive immunity provided from mother to child through
transplacental antibody transfer, childhood nutrition and national vaccination
36
schedules. The measles virus may ultimately be responsible for more child deaths
than any other single microbe - due to complications from pneumonia, diarrhoea
and malnutrition. Measles is a human disease and is not known to occur in animals.
Although vaccine initiatives have had considerable success in reducing its impact,
measles continues to be a serious global health burden. The disease cause more
than 130,000 deaths in 2010, mostly in low-income countries of Africa and Asia
(McMichael, Butler,). In addition to being an ongoing threat in the developing
world, developed nations that had achieved measles elimination in the 1990’s,
such as the United States, have recently experienced an increasing number of
outbreaks due to decreasing vaccination rates (US Environmental Protection
Agency, 2001).
In earlier studies, pre-vaccine measles incidence often exhibited a strong annual or
biannual pattern. Epidemics begin as early as September and as late as December
or January. The epidemics peak in the spring, often in late March or early April
(Fine & Clarkson, 1982).
Measles is a vaccine-preventable disease. Prior to the availability of measles
vaccine, measles infected over 90% of children before they reached 15 years of
age. Though childhood immunization program has markedly increases its coverage
in Bangladesh but still now it is one of the major causes of mortality and morbidity
in children. The United Nations selected routine measles vaccination coverage as
an indicator of progress towards Millennium Development Goal (MDG4), which
aims to reduce the overall number of deaths among children by two-thirds between
year 1990 and 2015 (Sustainable Measles Mortality Reduction; Regional Strategic
Plan 2007-2010 South East Asia Region, Jul 2007).
37
40
50
60
70
80
90
100
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
Percentage
0
5000
10000
15000
20000
25000
30000
Number of cases
Measles Case Measles vaccination coverage
Figure 1.7: Trend of Measles cases and Vaccination Coverage in Bangladesh
(Source: Bangladesh coverage evaluation survey 2011)
Measles outbreaks can be particularly deadly in countries experiencing or
recovering from a natural disaster or conflict. The major factors that determine the
epidemic spread of measles are the accumulation of the susceptible and new
migrant that have not suffered from disease in a community and the inevitable
exposure to infection.
Transmission
The highly contagious virus is spread by coughing and sneezing, close personal
contact or direct contact with infected nasal or throat secretions. The virus remains
active and contagious in the air or on infected surfaces for up to two hours. It can
be transmitted by an infected person from four days prior to the onset of the rash to
four days after the rash erupts. Transmission, which is primarily by large
respiratory droplets, increases during the late winter and early spring in temperate
climates and after the rainy season in tropical climates.
Measles outbreaks can result in epidemics that cause many deaths, especially
among young, malnourished children. Epidemics may still occur every 2 or 3 years
in areas where there is low vaccine coverage. According to the current measles
38
control strategy of Bangladesh measles outbreak is defined as an occurrence of 3
or more suspected measles cases in one month in a rural ward/urban mahalla.
Signs and Symptoms
The first sign of measles is usually a high fever, which begins about 10 to 12 days
after exposure to the virus, and lasts four to seven days. A runny nose, a cough, red
and watery eyes, and small white spots inside the cheeks can develop in the initial
stage. After several days, a rash erupts, usually on the face and upper neck. Over
about three days, the rash spreads, eventually reaching the hands and feet. The rash
lasts for five to six days, and then fades.
Picture 2: Picture of Measles like Cases in the Study Area
Severe measles is more likely among poorly nourished young children, especially
those with insufficient vitamin A, or whose immune systems have been weakened
by HIV/AIDS or other diseases.
Most measles-related deaths are caused by complications associated with the
disease. Complications are more common in children under the age of five, or
adults over the age of 20. The most serious complications include blindness,
encephalitis, severe diarrhoea and related dehydration, ear infections, or severe
respiratory infections such as pneumonia.
39
Picture 3: Complication of Measles like Cases
As high as 10% of measles cases result in death among populations with high
levels of malnutrition and a lack of adequate health care. People who recover from
measles are immune for the rest of their lives.
Prevention and control
The most effective way to prevent the disease or severe outcomes from the illness
is vaccination. Two doses of the vaccine are recommended to ensure immunity, as
about 15% of vaccinated children fail to develop immunity from the first dose.
1.8.2 Vector-borne Infectious Diseases
Insects, such as mosquitoes, ticks and fleas, are called “vectors” when they carry
diseases that can be passed on to animals or humans. An insect may contract a
disease when it bites an infected animal. If the insect then bites a human, the
disease is passed from insect to human. Different insects can carry different
diseases. Diseases associated with mosquitoes and fleas include malaria, dengue,
viral encephalitis and Kala azar. For humans to contract vector-borne diseases
usually require three conditions: 1) a human and/or animal “host” for the disease;
2) a large enough population of insects and, 3) a temperature range that supports
this population. Present climatic conditions allow for the survival of several
vector/rodent-borne diseases. Warmer temperatures associated with climate change
may enable vectors and the diseases they carry to extend their ranges and increase
40
their populations. As temperatures increase, the chance of humans contracting the
diseases may therefore also increase.
A changing climate can influence the spread of vector-borne diseases in several
ways. Firstly, climate determines the survival rates of bloodsucking insects,
particularly mosquitoes, fleas and ticks. For people who live in a cooler climate, it
is likely that mosquitoes are not around all year because winter freezing kills many
eggs, larvae and adults.
One study at Canada found that, in 30°C temperatures, greater than 90 per cent of
all mosquitoes contained infection after 12 days; at 18°C, less than 30 per cent
contained infection after 28 days. Therefore, diseases will reproduce faster inside
the vector as the climate warms. Increases in temperature can also affect vector
development and population growth. For example, high temperatures can increase
the rate at which mosquito larvae develop into adults. Faster adult development
means faster generational turnover, which means more mosquitoes.
Floods- another consequence of climate change could lead to mosquito
population booms. After floods recede, they leave behind standing water and
puddles perfect breeding grounds for mosquitoes. A growth in the population of
mosquitoes would create a greater opportunity for the spread of disease. Longer
summers and earlier springs would also extend the mosquito and fleas season.
The major vector borne climate sensitive disease in the study area is visceral
leishmaniasis (Kala-azar) and NIPAH virus infection.
Visceral Leishmaniasis (Kala-azar)
Visceral leishmaniasis (VL), also known as kala-azar, black fever, and Dumdum
fever, is the most severe form of leishmaniasis. Leishmaniasis is a disease caused by
41
protozoan parasites of the Leishmania genus. This disease is the second-largest
parasitic killer in the world (after malaria), responsible for an estimated 500,000
infections each year worldwide. An estimated 147 million people at risk in three
countries-Bangladesh, India, and Nepal, with about 100,000 cases occurring
annually (Goh, 2000). Kala-azar is a re-emerging disease and one of the major
public health problems in Bangladesh, and the disease has been endemic for many
decades. In Bangladesh about 40 million populations in 139 Upazilas and 45
districts are at risk (study area Rajshahi and Naogaon are within 45 districts). The
incidence is about 10000 cases every year in Bangladesh (Bangladesh Health
Bulletin 2012, Chapter 9). The parasite migrates to the internal organs such as liver,
spleen (hence 'visceral'), and bone marrow, and, if left untreated, will almost always
result in the death of the host. Signs and symptoms include fever, weight loss,
mucosal ulcers, fatigue, anemia, and substantial swelling of the liver and spleen.
Figure 1.8: Life-cycle of Kala-azar Parasite
Visceral leishmaniasis (Kala-azar) is spread through an insect vector, the sandfly
of the Phlebotomus genus. Sandflies are tiny creatures, 3–6 millimeters long by
42
1.5–3 millimeters in diameter, and are found in tropical or temperate regions
throughout the world. Sandfly larvae grow in warm, moist organic matter (such as
old trees, house walls, or waste) making them hard to eradicate.
Picture 4: Picture of Sand Fly
Favorable Conditions for Sand Fly Multiplication are:
monthly mean temperature between 7.2
0
- 37
0
C;
mean annual relative humidity (RH) of 70% to 80% RH at least for 3
months;
annual rainfall of 1250 mm or more;
altitude < 600 m;
alluvial soil;
high sub-soil water; and
abundant vegetation.
The adult female sand fly is a bloodsucker, usually feeding at night on sleeping
prey. When the fly bites an animal infected with L. donovani, the pathogen is
ingested along with the prey's blood.
43
Breeding Habit of the Sand Fly (P. argentipes)
P. a r g e n t i p e s breeds among debris
found in the corners of the soil floors
of rooms and cattle sheds as well as
under the feeding troughs. In
outdoor, larvae are found in the
cracks of the plinth made up of a
mixture of mud cow dung, on the
shaded side of huts and cattle sheds.
Picture 5: Breeding Place of Sand FlyResting Habit of Sand Fly (P. argentipes)
Sand flies are found to rest in cattle
sheds in much greater number than in
human dwellings. They take shelter
in dark corners settling on or under
cobwebs, in empty feeding troughs
and on any collection of straw or in
the cracks and crevices on the walls .
They also rest in chicken pens and
pigeon holes in small number.
Picture 6: Resting Place of Sand Fly
44
Seasonal variation of Kala- azar
P. argentipes generally disappears during the winter season i.e. November to
February. May be some decrease in June due to hot weather followed by an
increase with the advent of monsoon. The major peak density occurs in April to
May and minor peak densities are found in September to October.
Prevention and control of Kala- azar
In Bangladesh, Kala-azar patients are detected and treated mainly through primary
health care centers. ICT based rK39 strip is used for the diagnosis and oral
Miltefosine for the treatment of cases.
There is no vaccine for this disease.
Integrated vector management and environmental control is the main way to
prevent and control of this disease:
•
Indoor Residual Spray (IRS)-Two round a year (March-April & August-
September). Suitable chemical is pyrethroid
Picture 7: Insecticide Treated Nets with Synthetic Pyrethroid
•
Micro environmental Management through improved housing and living
conditions and reducing sand fly breeding places.
45
1.8.3 Emerging and Re-emerging Infectious Disease
Along with growing concern about the spread of existing diseases, comes the
threat of the introduction of new diseases as a result of warmer temperatures. For a
disease to be introduced to a region, the climate must be favorable for survival of
both the vector and the pathogen. An emerging or re-emerging infectious disease is
a disease whose incidence has increased in a defined time period and location. If
the disease was unknown in the location before, the disease is considered to be
emerging. However, if the disease had been present at the location in the past and
was considered eradicated or controlled, the disease is considered to be re-
emerging. Many of these emerging diseases are zoonotic, and rely on animal
populations as reservoirs of infection. Most emerging infections are caused by
pathogens already present in the environment, brought out of obscurity or given a
selective advantage by changing conditions and afforded an opportunity to infect
new host populations. These changes include ecological changes, such as those
due to human activities or to anomalies in climate; demographic changes and
behavior; travel and commerce; technology and industry; microbial adaptation and
change; and breakdown of public health measures. Many factors precipitate
emergence by placing humans or animals in contact with a natural reservoir or host
for an infection unfamiliar but already present (often a zoonotic or arthropod-borne
infection), either by increasing proximity or, often, also by changing conditions so
as to favor an increased population of the microbe or its natural host (Morse, 1996).
Diseases considered to be emerging or re-emerging include avian influenza, SARS,
Nipah, Chikongunia and Malaria.
46
NIPAH Virus Infection
Human Nipah virus (NIV) infection, an emerging zoonotic disease, caused by
Nipah virus originating from an new genus – the Henipa virus (Chua et al., 2000-
2003). Pteropus bats (Fruit bats) are the zoonotic host of the virus and pigs are the
likely amplifying host.
Picture 8: Picture of Pteropus Bats
Human infections range from asymptomatic infection to fatal encephalitis. Infected
people initially develop influenza-like symptoms of fever, headaches, myalgia
(muscle pain), vomiting and sore throat. This can be followed by dizziness,
drowsiness, altered consciousness, and neurological signs that indicate acute
encephalitis. Some people can also experience atypical pneumonia and severe
respiratory problems, including acute respiratory distress. Encephalitis and
seizures occur in severe cases, progressing to coma within 24 to 48 hours. The case
fatality rate is estimated at 40% to 75%; however, this rate can vary by outbreak
depending on local capabilities for surveillance investigations.
47
Natural host: Fruit bats of Pteropus family
Transmission
During the initial outbreaks in Malaysia and Singapore, most human infections
resulted from direct contact with sick pigs or their contaminated tissues.
Transmission is thought to have occurred via respiratory droplets, contact with
throat or nasal secretions from the pigs, or contact with the tissue of a sick animal. In
the Bangladesh and India outbreaks, consumption of fruits or fruit products (e.g. raw
date palm juice) contaminated with urine or saliva from infected fruit bats was the
most likely source of infection.
38
. Pteropus bats (Fruit bats) were found to be
positive for Nipah antibodies in different outbreak areas (Rahman et. al., 2012). Like
in other diseases caused by paramyxoviruses, such as measles, mumps, respiratory
syncytial virus infection, Para influenza, person-to-person transmission was a
common mode of transmission in Bangladeshi Nipah cases (Homaira et. al., 2007).
The virus was first recognized in a large outbreak of 283 reported cases in Nipah
village of Malaysia. After the large outbreak of Nipah encephalitis in Malaysia, only
three countries other than Bangladesh have been reported the outbreak, countries are
Singapore and India, all are in south asia (Chua et. al., 2000-2003, and Homaira et.
al., 2007). The Nipah cases were mostly distributed in the northwestern and central
part of Bangladesh, involving 20 districts. Outbreaks occurred during December to
May, which coincides with the winter season in Bangladesh. Therefore, it is
important to know whether specific climatic or host factors are responsible for
recurrent transmission of Nipah virus to human in Bangladesh.
48
Table 3: Shows Morbidity and Mortality due to Nipah or Nipah like Viral
Encephalitis in Bangladesh during the period from 2001 to 2011
Year/Month Location
No. of
cases
No. of
deaths
Case-fatality
rate (%)
April-May 2001 Meherpur 13 9
January 2003 Naogaon 12 8 67
January 2004 Rajbari 31 23 74
April 2004 Faridpur 36 27 75
Jan-March 2005 Tangail 12 11 92
Jan-Feb 2007 Thakurgaon 7 3 43
March 2007 Kustia, Pabna, Natore 8 5 63
April 2007 Naogaon 3 1 33
February 2008 Manikgonj 4 4 100
April 2008 Rajbari and Faridpur 7 5 71
January 2009 Gaibandha, Rangpur, Nilphamary
Rajbari
3
1
0
1
0
100
Feb-Mar 2010 Faridpur, Rajbari, Gopalgonj and
Madaripur 16 14 87.5
Jan-Feb 2011 Lalmonirhat, Dinajpur,
Nilphamari and Rangpur 44 40 83
Prevention and Control Nipah Infection
There are currently no drugs or vaccines available to treat Nipah virus infection.
Intensive supportive care with treatment of symptoms is the main approach to
managing the infection in people. In the absence of a vaccine, the only way to
reduce infection in people is by raising awareness of the risk factors and educating
people about the measures they can take to reduce exposure to the virus.
•
Reducing the risk of bat-to-human transmission. Efforts to prevent
transmission should first focus on decreasing bat access to date palm sap.
Freshly collected date palm juice should also be boiled and fruits should be
thoroughly washed and peeled before consumption.
49
•
Reducing the risk of human-to-human transmission. Close physical contact
with Nipah virus-infected people should be avoided. Gloves and protective
equipment should be worn when taking care of ill people. Regular hand
washing should be carried out after caring for or visiting sick people.
1.9 Background on Climate Change and Health Impacts in Bangladesh
Bangladesh is one of the countries which have been significantly affected by
natural disasters. In recent times natural hazards are more frequent and intense. It
is now accepted, mainly by the IPCC scientists and national governments, that this
climatic hazards are the results of climate change at global and regional level.
IPCC states in their third (2001) and fourth assessment (2007) reports that the
global average surface temperature has already increased by 0.6
0
C (+/- 0.2
0
C)
during last 140 years and 0.74
0
C (+/- 0.18
0
C) during the last 100 years
respectively and likely to increase from 1.4 to 5.8
0
C by 2100. For Bangladesh, the
projections show that by 2030, a 0.7
0
C temperature raise in monsoon season and a
1.3
0
C rise in the winter season might take place.
According to IPCC (2001), global warming would cause increase of vector borne
and water borne diseases in the tropics (IPCC, 2001). All around the world,
increased natural, technological and human induced hazards have brought along
frequent epidemics, increased number of deaths, injuries and health problems of the
human beings. Moreover, non-climate issues including poor housing, lack of safe
water and sanitation facilities, inadequate or improper health care services would
increase the adversity of health problems. Many scientists have already anticipated
that more frequent and more intense or severe weather events will result in increased
deaths, injuries and diseases in developed countries like Canada, but the biggest
impact will be felt in low-lying, heavily populated areas such as Bangladesh,
particularly when coupled with sea level rise (Canadian Association of Physicians
50
for the Environment, 2006). Estimation shows that at least 3000 million people of all
tropical countries are exposed to the risk of dengue while 2400 million tropics and
subtropics are at risk of malaria (IPCC, 2001; Githeko and Woodward, 2003). Other
sources estimate that climate change causes 2.4 per cent of all cases of diarrhea
worldwide and 2 percent of all cases of malaria (WHO, 2006). It was also estimated
that climate changes was responsible for at least 150,000 deaths and 5.5 million
Disability Adjusted Life Years in the year 2000.
The arrogant Himalayas in the north and funnel shaped Bay of Bengal in the south
have made a meeting place of the life- giving monsoon rains and the catastrophic
devastation of floods, cyclones, storm surges, droughts etc. (Paramanik, 1991). A
recent study shows that at least 174 natural disasters affected Bangladesh from
1974 to 2003 (Sapir et. al., 2004). Extreme events such as floods, drought and
cyclone etc. directly and indirectly affect health of people of this country almost
every year (Annex-). For example, the total death caused by flood in 2004 was
about 800 while cyclone of 1991 killed 138,000 people of Bangladesh (ADB,
2004; BCAS, 1991).
Bangladesh is already vulnerable to outbreaks of infectious, water borne and other
types of diseases (World Bank, 2000). Other diseases like diarrhea, dysentery, etc.
are also on the increase especially during the summer months. It has been
predicted that the combination of higher temperatures and potential increase in
summer precipitation may cause spread of many infectious diseases (MoEF,
2005).Climate change also brings about additional stresses like dehydration,
malnutrition and heat related morbidity especially among children and the elderly.
These problems are thought to be closely interlinked with water supply, sanitation
and food production. Climate change has already been linked to land degradation,
freshwater decline, biodiversity loss and ecosystem decline, and stratospheric
51
ozone depletion. Changes in the above factors may have a direct or indirect impact
on human health as well.
There were some researches and studies on climate change and its impacts in
Bangladesh at different times by both government and non-government
organizations/institutions. But research on human health impacts due to climate
change in Bangladesh has not gained much focus before 2006. Climate Change
Cell (CCC) under Comprehensive Disaster Management Programme (CDMP) has
brought climate change and health as priority issue for research in 2006.
In order to have a better understanding of the possible link between climate change
and human health this study will give us a better picture of present status of
infectious disease burden of the district. Understanding the burden of these
diseases can inform rational allocation of health resources and also to take special
initiatives to improve the situations. So the present research may provide the
linkage between climate change and infectious disease outbreak in children that
helps environmentally friendly public health interventions.
1.10 Objectives of the Study
The overall objective of the study is to find out the impact of climate change on the
outbreak of infectious diseases among children in Bangladesh: its prevention and
control. However, the specific objectives are:
• To investigate the causes of diseases among children in relation to climate
changes.
• To investigate the outbreak of diseases among children in relation to
climate changes.
• To estimate the incidence of vaccine preventable disease and determine
their extent and distribution.
52
• To evaluate the immunization status.
• To observe the pattern of climatic change in the study areas
• To compare the disease pattern with seasonal variation.
1.11 Scope of the Study
The study included the rural and urban areas in two climate sensitive district of the
country. Rajshahi division has a tropical wet and dry climate. The climate of
Rajshahi is generally marked with monsoons, high temperature, considerable
humidity and moderate rainfall (Banglapedia, 2004). Two districts Rajshahi and
Naogaon were selected to assess the health impacts on the outbreak of infectious
diseases among children due to climate change and climate variability as well as
their correlation. Both the district has drought prone barind areas, plane land and
low land.
However, the following steps describe the scope of the study
• Identification and investigation of diseases and outbreak of diseases that are
most closely related to climate change and are prevalent in the study areas.
• Collection of vaccine preventable disease data from routine vaccination site,
Upazila health complex, district hospital and Medical college hospital.
• Collection of annual and seasonal data on the occurrence of vector, water
and air borne disease in order to build up a database. These were related to
specific climate data like temperature and rainfall. This primary data were
collected from Upazila health complex, district hospital, Medical college
hospital and private medical practitioners in the study areas.
•
Interviews with health professionals that includes doctors, nurses, health
workers, NGO workers and community people during outbreak and disease
investigation.
Chapter Two
Materials and Methods
The methodology of the study includes analysis of both secondary and primary
data. Infectious disease related data were collected from Upazila Health Complex,
Civil Surgeon office, City Corporation of the study area and also from MIS of
DGHS, Dhaka. Time series of climate factors data were collected from Bangladesh
Meteorological Department Dhaka and from local weather station, Rajshahi.
Statistical software SPSS used to find out the correlation association between
climatic variables temperature, rainfalls and incidence of infectious diseases
(diarrhea, measles, kala-azar). In addition, immunization status and incidence of
vaccine preventable infectious disease also analyzed. Primary data collection tools
include household survey, active case search at hospital facilities and in-depth
interview with diseased individual or from attendant. The main purpose of primary
data collections were to collect the data on infectious disease (present and past),
vaccination status of the children, perception on climate variables (temperature,
rainfall), seasonal changes of climate factors etc.
2.1 Descriptions of the Study Area
Rajshahi District
Rajshahi district is a district in north-western Bangladesh and a part of the
Rajshahi Division. Rajshahi has one city corporation, 9 upazilas, 72 union
parishads, 1678 mouzas and 1858 villages. Upazillas of Rajshahi are: Bagha,
Bagmara, Charghat, Durgapur, Godagari, Mohanpur, Paba, Puthia and tanore.
54
Map 3: Map of Rajshahi district
Area: 2463.01 sq km.
Weather: Annual average temperature of this district is maximum 37.8°C,
minimum 11.2°C. Annual rainfall is 1862 mm.
Boundary: Rajshahi district is bounded by Naogaon district on the north, Natore
district on the east, Chapai Nababganj district on the west and the river Padma to
the south.
Main Rivers: There are ten rivers; main rivers are Padma (Ganges), Mahananda,
Baral and Barnai.
Population: 2262483; male 51.20%, female 48.80%.
Religion: Muslim 93%; Hindu 5%, Christian 1.5% and others 0.5%.
Ethnic national: Santal 2.34%.
55
Literacy rate: 30.61%; male 37.6% and female 23.2%.
Main occupations: Agriculture 38.73%, agricultural labourer 23.64%, commerce
12.44%, service 8.81% etc.
Main crops: Paddy, wheat, jute, sugarcane, turmeric, oil seed, onion, garlic,
potato, betel leaf and mulberry plant.
Naogaon District Information
Naogaon district in the Northern Bangladesh within the Rajshahi Division. It
consists of 11 upazilas, 99 union parishads and 2795 villages. Boundary: Naogaon
district is bounded by West Bengal of India on the north, Natore and Rajshahi
districts on the south, Joypurhat and Bogra districts on the east, Nawabganj district
and West Bengal (India) on the west.
Map 4: Map of Naogaon district
56
Area: 3449 sq km
Weather: Annual temperature is maximum 37.8°C and minimum 11.2°C.
Annual rainfall: 1862 mm.
Major rivers: Atrai, Punorvoba, Nagor, little jamuna, Chiri and Tulsiganga.
Population: 2377314. Male 50.66% and female 49.34%
Religion: Muslim 84.51%, Hindu 11.39%, others 4.1%
Ethnic community: Santal, Oraon ,Mahali,Munda, Mahali, Bansphor and Kurmi.
Literacy rate: Average literacy 28.4%; male 35.9% and female 20.4%.
Main occupations: Agriculture 49.01%, agricultural laborer 26.96%, commerce
8.35% etc.
Main crops: Paddy, potato, watermelon, oil seeds, pulses etc.
Main exports: Paddy, rice and potato.
Economic importance of Naogaon:
Naogaon is considered the storage of food supply for Bangladesh. Here, local
peoples are mostly farmer.
2.2 Secondary Data Collection
A number of health related documents and climate change data were collected
from concerned local, regional and national sources. Time series (Year 1964 to
2011) temperature and rainfall data were collected from Bangladesh
Meteorological Department (BMD) Dhaka and local weather station Rajshahi. It is
also essential to mention that there were some missing data in some months. Data
were considered to be missing when the data were not recorded. To maintain the
continuity, the gaps were filled up by the time mean values of the existing years.
Health related documents were collected from MIS of Director General (DG)
Health of Ministry of the Health and Family Welfare of the Government of
Bangladesh (GoB). Time series of disease record were collected from Upazila
57
Health Complexes (UHC), Sadar Hospital, City Corporation, Municipality and
Civil Surgeon Office of the study districts. Time series of diseases were available
for 12 years.
2.3 Primary Data Collection
Multiple methods were used to collect primary data. These are as follows:
• Sample survey
• In-depth Interview during outbreak investigation and searching
The sample survey was designed to assess the vaccination status of 9 months to
under 5 years children in the study districts.
Sample Survey
The sample survey was carried out in the households of the villages/mouzas
of nine Upazila and one City Corporation of Rajshahi district and eleven Upazila
and one municipality of Naogoan district by using the 30 cluster coverage survey
sampling technique. Sampling units were selected according to population
proportionate to size (PPS) method (BBS and WHO standard). Using the 30-
cluster survey sampling technique, 30 clusters sampled from each survey unit for
each district. The 30 clusters were selected by using the systemic random sampling
technique. For selecting 30 clusters of a district, Village/mouzas was used as the
primary sampling unit. In a sampling unit, survey start from the central part of the
village /mouza, randomly choose a direction, randomly select a household and
conduct interviews in consecutive households for 7 eligible respondents (9 months
to under 5 years children) along with information on the age composition of target
samples and the total household population. Mother of the child was given priority
to respond to the questions. In absence of mother other senior person of household
was requested to respond. Sometime they all discussed before responding to some
58
question particularly on health disorders and climate change issues. The
questionnaire generally focused on the vaccination status of the children, education
and occupation of parents, knowledge about climate change and infectious disease,
experiences of Infectious disease within one year and monthly family income.
Picture: 9 & 10- Interviewing mother regarding infectious disease and climate
change knowledge in community household and clinic setup.
The questions were both open and closed ended. (Please see annex-i). For this
study sample, a total of 60 sampling unit selected from the two selected district.
The total respondent for sample survey was 420.
In-depth Interview
A prescribed format used to collect weekly infectious disease report from the 21
survey units. Active case search at government and NGO facilities. Used standard
WHO case definition of the diseases for diagnosis, notification and declaration of
an outbreak. In-depth interviews were taken from the diseased individual or from
attendant about clinical course of disease, time of onset of disease, epidemiological
linkage, knowledge about climate change and vaccination status of the patient.
59
Picture-11: Interview mother about the outbreak of disease.
Picture-12: Collection of blood sample from patient in the community.
In response to notification of an outbreak of disease a pre investigation orientation
was arranged for the search team, comprising of field worker and investigator
himself. Investigator assist to train the whole team with objectives of the outbreak
investigation, case definition, blood sample collection, methods of data collection
including the prescribed forms. (Please see the annex-ii, iii). The door to door
approach was adopted throughout the whole rural and urban ward to collect the data.
60
Picture-13: Blood sample centrifuge to prepare serum
Picture 14: Cold chain box with centrifuge serum for transportation
After collection of blood sample from the patient serum was separated by
centrifuge machine and shifted in to special sterilize container. For serum
separation blood sample was settled for half an hour and spanned in centrifuge
machine for 20 minutes. Then sterilize container with 1 ml serum labeled properly
with patient’s ID no, name, age, sex, address and was placed into cold box. With
61
maintaining cold chain (+2
0
C to +8
0
C) specimen sent to Institute of Public Health
for testing. Measles and Rubella Immunoglobulin “M” (IgM) identifying reagent
used in the laboratory.
Picture-15: Serum sample tested for measles and rubella specific IgM antibody
Immunization status observation method
For protection against the eight deadly childhood diseases, namely tuberculosis,
diphtheria, pertussis, tetanus, Hepatitis-B (Hep-B), Hemophylus Influenza Type-B
(Hib), poliomyelitis and measles, WHO recommends that each child be immunized
with one dose of BCG against tuberculosis, three doses of Penta against diphtheria,
pertussis, Hep-B, Hib and tetanus, four doses of Polio Vaccine (OPV) against
poliomyelitis, and one dose of Measles vaccine against measles. It also
recommended that all the antigens be administered to the child by the first birthday
according to the following schedule: BCG at or after birth; Penta1/OPV1 at the age
of six weeks or after; Measles vaccine at the age of 270 days or after. The interval
between the consecutive doses of Penta/OPV should be four weeks or more meaning
that Penta2/OPV2 should be given four weeks or more after Penta1/OPV1 and
Penta3/OPV3 should be given four weeks or more after Penta2/OPV2.
62
Picture 16: Interviewing mother regarding vaccination status of the children
To assess the vaccination status of children in the study area, only valid
vaccination coverage was assessed. Valid coverage was assessed in terms of valid
doses of any antigen administered to a child by age one year. A valid dose was a
recommended dose of a recommended antigen administered in a recommended age
and or intervals. Considering the above schedule vaccination related information’s
were collected from 60 clusters of study districts through house survey.
Chapter Three
Results
The study area Rajshahi and Naogaon are the western districts known barind area
in Bangladesh and poses drought prone plane, riverine and low lands. Time series
data on climate factors like temperature and rainfall of Rajshahi station and
infectious diseases data/information specially climate sensitive diseases viz.
diarrhea, malaria, dengue, measles, kala azar and nipah virus infection were
considered for interpreting their correlations as described below:
Analysis of Secondary data
3.1 Climate Characteristics (Temperature and Rainfall)
The time series climatic data comprised monthly and annual mean, maximum and
minimum temperature for the period of 1964-2011 and monthly and annual mean
rainfall for the period of 1964-2011. The data were analyzed to find the seasonal,
intra-seasonal and annual changes.
The long-term changes of annual maximum, mean and minimum temperature of
study area over the study period (1964-2011) (Figure 3.1), (Appendix-1- 3) found
to have in general increasing trends in annual mean and annual mean minimum
temperature but the mean maximum temperature slightly was decreasing in recent
past decades. The study revealed that through the last 47 years (1964-2011) the
annual mean temperature, annual mean minimum temperature has increased by
1.1
0
C and 3.5
0
C respectively but the annual mean maximum temperature has
decreased by 4.7
0
C.
64
Figure-3.1 The annual mean minimum, mean and mean maximum
temperatures in Rajshahi region during the period 1964-2011.
The long-term seasonal mean temperatures are also found to have increasing trend
over the study period (1964-2011) (Figure 3.2) and Appendix-1-4. The highest
average maximum temperature was 30.55
0
C observed in the month of April in pro
monsoon season and the lowest average temperature was 15.45
0
C in the month of
January in winter season.
Figure-3.2 The annual winter mean, monsoon mean and summer mean
temperatures in Rajshahi region during the period 1964-2011.
65
The figure 3.3, Appendix-3 indicates that the long-term monthly minimum
temperature in the study area over the study period (1964-2011) was lowest in the
month of January and December which corresponds to the coldest months
observed in winter season of Bangladesh.
Figure-3.3 Monthly average maximum and minimum temperatures in
Rajshahi region during the period 1964-2011.
The figure 3.3, Appendix-2 also shows that the long-term monthly maximum
temperature in the study area over the study period (1964-2011) is highest in the
month of April and May which corresponds to hottest months observed in
summer/pre monsoon season of Bangladesh.
Trends in Rainfall in Study Area
The long-term changes in annual rainfall in the study area over the period (1968-
2011) showed (Figure 3.4), Appendix-5 declining trends from last two decades.
The average annual rainfall was 1489 mm/year.
66
Figure-3.4 Annual average rainfall in Rajshahi during the year 1964-2011
The long-term seasonal rainfall in the study area (Figure 3.5), Appendix- 6
showing markedly reduced in winter and post autumn season. Most of the rainfall
occurred in monsoon season that is also declined in the study area over the study
period (1964-2011).
Average rainfall 1489 mm/year
Time series
67
Figure-3.5 Annual winter and summer rainfall in Rajshahi during the
year 1964-2011
Figure-3.6: Annual monsoon and post monsoon rainfall in Rajshahi
during the year 1964-2011
The average seasonal rainfall in the study area in the study period 1964-2011
during winter, summer, monsoon and post monsoon were 30.10 mm, 216.79 mm,
1222.37 mm and 131.56 mm respectively.
68
3.2 Climate Sensitive Infectious Disease Profile
The major climate sensitive disease data/information was collected from 20
Upazilla Health Complex (UHC), 01 Municipality and 01 City Corporation health
authorities, 02 Civil Surgeon offices and also from MIS DG-Health, Dhaka office.
It may be noted that disease data up to the year 2008 were collected from DG-
Health Dhaka and later on (2009-2011) all the incidences of climate sensitive
infectious diseases and their outbreak report were collected from all the UHC,
Municipality, City Corporation, Sadar Hospital and Civil Surgeon office by using
specific weekly disease report format (appendix-iv).
In Bangladesh a good number of people suffer from diarrhoea, ARI, malaria,
measles, kala azar, dengue and other infectious disorder. The following table and
figures show the annual incidence of some of the major climate sensitive diseases
and their trend in Bangladesh.
Table-3.1 Incidence of some major climate sensitive diseases in Bangladesh
adapted from DG-Health bulletin 2012
SL Disease Incidence Duration Average incidence per year
1 Diarrhoea 28166084 Year 1999- 2011 2166521
2 Kala azar 1062 38 Year 1994- 2011 5902
3 Malaria 1534864 Year 1992- 2011 76743
4 Measles 136551 Year 1990- 2011 6502
5 Dengue 25413 Year 2000- 2011 2118
6 NIPAH 197 Year 2001- 2011 18
69
Figure-3.7 Incidence of diarrhoea in Bangladesh during the period of 1999-2011
Figure-3.8 Incidence of Kala azar in Bangladesh during the period of 1994-2011
70
Figure-3.9 Incidence of NIPAH in Bangladesh during the period of 2001-2011
Figure3.10. Incidence of Measles like cases in Bangladesh during the period of
1990-2011
71
Seasonal incidences of climate sensitive infectious diseases and their outbreak in
each year over the study period were also observed. To explore the association
between climate sensitive infectious diseases and climate factors correlation
analysis was carried out using both secondary and primary data. Climate factors
such as annual and seasonal rainfall, annual mean maximum and minimum
temperature and climate sensitive diseases (e.g. Diarrhoea, Kala azar, Measles)
were analyzed to find out the association between impacts of climate change on
the outbreak of infectious diseases in the study area. Pearson’s coefficient was
applied to detect the extent of association between incidences of each disease and
climate factors. Data on climate factors and incidences of climate sensitive
infectious diseases from year 2000 to 2011 were used to find out the correlation.
A positive correlation implies that the greater the variation in the climatic factors
the larger the number of incidences of diseases. The results of the correlation
analysis between climate factors and climate sensitive infectious diseases are
individually shown below with disease discussion
Diarrhoea
The incidences of diarrhoea have declined over time in Bangladesh. According to
BDHS data 2007, the incidence rate is highest in Chitagong, Dhaka and Sylhet
divisions (around 11 percent), while Rajshahi division reports the lowest incidence
(7.6 percent). Figure-3.11 and appendix- 7 showed the annual incidence of
diarrhea in the study area over the study period found similarities with the national
findings.
72
Figure-3.11 Annual incidence of diarrhoea in the study area during the period
of 2000 to 2011
The Figure 3.12-3.14 and table-3.2 show that the incidences of diarrhea have
positive correlation with annual and seasonal rainfall and with both mean
maximum and minimum temperature. The highest number of diarrhoea cases
(39092 cases) and highest rainfall (1786 mm) was reported from the study area in
the year 2004.
Figure-3.12 Trends of annual rainfall and diarrhoea incidences in the study
area during the period of 2000 to 2011
73
Figure-3.13 Trend of annual average maximum temperature and diarrhoea
incidences in the study area during the period of 2000 to 2011
Figure-3.14 Trend of annual average minimum temperature and diarrhoea
incidence in Study area during the period of 2000 to 2011
74
Table-3.2 Values of Correlation coefficient of climatic variables and diarrhoea
in study area during the study period (2000-2011)
Correlation on incidence of Diarrhoea and climatic factors
Sl.
No Climatic variables Disease
Value of
Correlation
coefficient
A Total annual rainfall (N=12) Diarrhoea +0.016
B Total seasonal rainfall (N=12)
1 Winter (Dec, Jan, Feb) Diarrhoea +0.193
2 Summer or Pre-monsoon (March, April, May) Diarrhoea +0.065
3 Monsoon (June, Jul, Aug, Sept) Diarrhoea +0.132
4 Autumn or Post monsoon (Oct, Nov) Diarrhoea +0.060
C Annual average maximum temperature (N=12) Diarrhoea +0.014
D Annual average minimum temperature (N=12) Diarrhoea +0.002
From above table incidences of diarrhea were found to have positive correlation
(+0.016) with total annual rainfall and total winter (+0.193), summer (+0.065),
monsoon (+0.0132) and total post monsoon (+0.060) seasonal rainfall over the
reported period. Occurrence of diarrhea remained highest during monsoon in most
of the year. The highest correlation found with total seasonal winter rainfall (+0.193)
and lowest with annual average minimum temperature (+0.002) in the study area.
Kala-azar/Leishmaniasis
Kala-azar is one of the major neglected disease in the world which been heavily
impacted by the global climate change. The climate of Bangladesh is also
changing which making people more prone to infectious diseases. The study area
Rajshahi and Naogaon district are kala-azar endemic district in Bangladesh
(Bangladesh Health Bulletin, 1998).
75
Kala-azar incidences, climatic factors (rainfall and temperature), vectors breeding
sites were collected from 20 Upazila of study districts. Relationship between kala-
azar patient and their distribution were evaluated.
Figure-3.15 Incidence of Kala-azar in study area during the period of 2001 to 2011
Figure-3.16 Seasonal incidence of Kala-azar in study area during the period
of 2001 to 2011
76
Figure- 3.15, 3.16 and appendix tables-8 show the yearly and seasonal incidences
of kala-azar in the study areas. The incidences of kala-azar found highest in
monsoon season in the month of July, August, October and November and
declined in winter months of December, January and February.
Pearson’s correlation was calculated for the number of kala-azar patients of each
season with annual and seasonal rainfall and with average maximum and minimum
temperature. Kala-azar was found (Table-3.3) to have positive correlations with
both annual and seasonal rainfall and annual average maximum temperature. In
winter there were significant positive impacts of rainfall with the increased number
of kala-azar patient. Negative correlation also found between kala-azar and annual
average minimum temperature in the study period.
Figure3.17. Trend of annual rainfall and Kala-azar incidences in the study
are during the period of 2001 to 2011
77
Table-3.3 Values of Correlation coefficient of climatic variables and Kala azar
in study area during the study period (2000-2011)
Correlation on incidence of Kala azar and climatic factors
Sl.
No Climatic variables Disease
Value of
Correlation
coefficient
A Total annual rainfall (N=12) Kala azar +0.498
B Total seasonal rainfall (N=12)
1 Winter (Dec, Jan, Feb) Kala azar +0.937
2 Summer or Pre-monsoon (March, April, May) Kala azar +0.715
3 Monsoon (June, Jul, Aug, Sept) Kala azar +0.998
4 Autumn or Post monsoon (Oct, Nov) Kala azar +0.567
C Annual average maximum temperature (N=12) Kala azar +0.609
D Annual average minimum temperature (N=12) Kala azar -0.635
Table-3.3 and Figure 3.18 and 3.19 showed that kala-azar have positive correlation
with both annual and seassonal rainfall.The highest correlation (+0.998) of kala-
azar incidence was observed with total monsoon rainfall, then dry winter rainfall
(+0.937) and lowest (+0.567) at post monsoon rainfall.
Figure 3.18 Trend of annual mean maximum temperature and Kala-azar
incidences in the study are during the period of 2001 to 2011
78
Figure-3.19. Trend of annual mean minimum temperature and Kala-azar
incidences in the study are during the period of 2001 to 2011
The incidence of kala-azar and climate factors for the period of 2001-2011
represented in Figure-3.18 and 3.19 have positive correlation (+0.627) with annual
mean maximum temperature and negative correlation (-0.68) with annual mean
minimum temperature.
The present data showed significant co-relationship between climatic factors and
kala-azar incidences in study area.
Measles
Figure 3.20 shows most of the outbreak occurs in March, April and May, whereas
number of cases highest in April, May and June. These 4 months corresponds to
the summer season of Bangladesh. Measles were found (Table-3.4) to have
positive correlation with both seasonal rainfall and annual average maximum
temperature and negative correlation with annual rainfall. In winter there were
significant positive impacts of rainfall with the increased number of patient.
79
Negative correlation also found between measles like diseases and annual average
minimum temperature in the study period.
Figure-3.20 Incidence of Measles outbreak and cases in study area during the
study period
Figure-3.21 Seasonal trends of Measles cases in study area during the study period
80
Table-3.4 Values of Correlation coefficient of climatic variables and Measles
in study area during the study period (2000-2011)
Correlation on incidence of Measles and climate factors
Sl.
No Climate variables Disease
Value of
Correlation
coefficient
A Total annual rainfall (N=12) Measles -0.475
B Total seasonal rainfall (N=12)
1 Winter (Dec, Jan, Feb) Measles +0.899
2 Summer or Pre-monsoon (March, April, May) Measles +0.233
3 Monsoon (June, Jul, Aug, Sept) Measles -0.131
4 Autumn or Post monsoon (Oct, Nov) Measles +0.1000
C Annual average maximum temperature (N=12) Measles +0.967
D Annual average minimum temperature (N=12) Measles -0.003
The incidences of measles like cases were found to have positive correlation with
annual average maximum temperature (+0.967) and seasonal winter (+0.0899),
summer and post monsoon (+0.1000) rainfall. Negative correlation were found
with total annual rainfall (-0.0475), seasonal monsoon rainfall (-0.131) and annual
average minimum temperature (-0.003).
3.3 Results from Primary Data
This section deals with findings of 60 cluster sample using 30 cluster survey
technique in two study districts and all reported infectious disease outbreak in the
study period. In each cluster 7 household’s respondent were included. The sample
survey included a total of 420 households. Some demographic information and
vaccination status of less than 5 years children were also recorded during house to
house survey. The findings of the study have been assessed quantitatively and
81
qualitatively to find correlation between impact of climate change and outbreak of
infectious diseases among children.
3.3.1 Socio-Demographic Profile of the Study Area
The socio-demographic status of households in the study area has been recorded.
The demographic factors of the households covered in the study area include age,
sex, education of the respondents (child’s mother), profession, health etc. The
variables have been described in the following sub-sections:
Household Size and Sex Ratio in the Study Area
The cluster household survey of study area reveals that the average household size
(the number of person per household) was 5.1. The male members of households
were slightly higher than female. Male constituted 51.9 percent of household
members while 48.1 percent were female (Figure 3.22). However, the survey
reveals that the total number of members of households varies from cluster to
cluster unit.
Figure-3.22 Distribution of household members by sex in study area
82
Household Members by Age Group
It was found that the age of maximum number of household members (51.4%) of
study area ranged between 16-60 years (Figure-3.23). The second highest category
of the study households were between 5-15 years (18.3%), while 10.7% population
more than 60 years, 4.8% was under 1 year and 14.8% between 1-4 years. As the
study was designed to survey those households which have at least one child
within 5 years old, so the age group of the study area may not reflect the normal
age group scenario.
Figure-3.23 Percent distribution of household member by age group in study area
Education of Respondent Mother
It was found that 71% of respondent’s mother finished primary education, 2%
were illiterate while 19% passed SSC and 6% passed HSC level. The rest 2 percent
of the respondent mothers having graduate and higher degrees (Figure3.24).
83
Figure-3.24 Percent distribution of respondent mother by education in Study Area
3.3.2 Common Infectious Diseases in the Study Area
The common infectious diseases which affected the household members especially
children including diarrhoea, common cold/cough/fever, measles like disease
(locally known as Kheshra/Koda), skin disease, kala-azar, jaundice. Although the
household respondents identified various diseases in the study area but here the
analyses mainly focused on climate sensitive disease among children. According
to response of households (Figure-3.25, Appendix-9), diarrhoea was identified as
common disease among children as mentioned by 86 percent respondents in the
study area while 7 percent of the respondent mother mentioned about measles like
disease, jaundice 6 percent and kala-azar 1 percent. On the other hand, most of the
respondents of the entire survey unit identified cough/cold/fever as a common
infectious disease among children.
84
Figure-3.25 Incidences of Infection Diseases among Children in Study Area
3.3.3 Respondents’ Opinion on Possible Reasons for Disease Incidence
The respondent responses regarding the possible causes of major infectious
diseases in the study area were analyzed and it was found that most of the
childhood infectious diseases like diarrhoea, measles like disease, common cold,
cough, fever and kala-azar have association with climatic variables. According to
the opinion of respondents’ of all cluster samples, temperature variation causes
most of the diseases incidence and others significant reasons include rainfall
variation, water pollution and natural disaster. With regard to causes of diarrhoeal
incidences, 44% are attributable to change in temperature, followed by 29% to
rainfall variation, 13% to water pollution and 8% to natural hazards. Most of the
respondent, 74% mentioned temperature variation as cause of measles like disease.
While 3%, 8% and 4% respondent mentioned rainfall variation, natural hazards
and other factors as causes respectively. Among the respondents, 41%, 33%, 3%,
3% and 14% respectively mentioned that temperature; rainfall, natural hazards,
water pollution and others (poor sanitation and housing) were the causing factors
for kala azar. (Figure 3.26-3.28, Appendix-9)
85
Figure-3.26 Causes of diarrhoea according to percent respondents
Opinion in the study area
Figure-3.27 Causes of measles according to percent respondents Opinion in
the study area
86
Figure-3.28 Causes of Kala-azar according to percent respondents Opinion in
the study area
3.3.4 Incidence of Infectious Diseases over last 10 years
Regarding incidence of infectious diseases in last 10 years, most of the
respondents mentioned about highest incidence of diarrhea (81 percent) and
ARI/cough and cold (87 percent) while 11 percent and 1 percent respondents
observed measles like disease and kala-azar respectively which affected their
family members in last 10 years. Among 420 respondents, only one respondent in
the study area mentioned about Nipah virus infection that affected one of their
family member in last 10 years.
3.3.5 Respondents’ Knowledge and Understanding on Climate Change
Understanding on the term “climate change” among the respondents of the
households in the study area was not very satisfactory. The findings show that only
17 percent of the respondents could appropriately mention about the term of
climate change. However, most of the respondents have the clear cut ideas about
season of Bangladesh.
87
3.3.6 Vaccination Status of Children in the Study Area
To assess the vaccination status of children in the study area, only valid
vaccination coverage was assessed. Valid coverage was assessed in terms of valid
doses of any antigen administered to a child of one year age. A valid dose was a
recommended dose of a recommended antigen administered in a recommended age
and or intervals. For the protection of children, government of Bangladesh
introduced routine immunization against deadly infectious diseases of children,
namely childhood tuberculosis, diphtheria, pertusis, tetanus, hepatitis-B,
hemophylus influenza type B (HiB), polio and measles. WHO recommends that
each child be immunized with one dose of BCG against tuberculosis, three dose of
penta against diphtheria, pertusis, tetanus, hepatitis- B and HiB, 4 dose of polio
against poliomyelitis and one dose of measles vaccine against measles. It also
recommends that all the antigen be administered to the child by the first birthday
according to the following schedule: BCG at or after birth; Penta1/OPV1 at the age
of six weeks or after; Measles vaccine at the age of 38 weeks or after. The interval
between the consecutive doses of Penta/OPV should be four weeks (28 days) or
more meaning that Penta2/OPV2 should be given four weeks (28 days) or more
after Penta1/OPV1 and Penta3/OPV3 should be given four weeks (28 days) or
more after Penta2/OPV2. Considering the above schedule vaccination data were
collected, collate and found almost all the children got access to vaccination
service. Data showed BCG coverage was 100 percent while penta1, penta2, penta3
and measles coverage were 99 percent, 96.60 percent, 92.40 percent and 86.20
percent respectively (Figure 3.29).
88
Figure-3.29 Vaccination status (%) of children bellow one year of age in the
study area
3.3.7 Incidence of Vaccine Preventable Diseases in Study Area over the
Study Period
It was found that there was no incidence of childhood tuberculosis, diphtheria,
poliomyelitis and pertusis in the study area within the study period while 4
neonatal tetanus cases, one in year 2009, two in year 2010 and one in 2011 were
reported (Table-3.5). The incidence rate of neonatal tetanus (NT) in the study area
was 0.012/1000 live birth per year that is neonatal tetanus incidence rate met
national target (national target is 1 or more/1000 live birth).
Table-3.5 Vaccine Preventable Diseases in the Study Area
Diseases Year 2009 Year 2010 Year 2011 Total
<5 Tuberculosis 0 0 0 0
Diphtheria 0 0 0 0
Pertusis 0 0 0 0
Neonatal Tetanus 1 2 1 4
Poliomyelitis 0 0 0 0
Measles 78 54 104 236
89
3.3.8 In-depth Investigation of Reported Outbreak in the Study Area
During in-depth investigation of reported outbreak a prescribed line listing form
was used (Appendix-ii, iii) and interviewed all the outbreak related personnel
about the course of disease and their link with climatic variables. Regarding
climatic variables, most of the respondent’s mentioned that there is change in
seasonal temperature, rainfall, humidity etc. Many of the respondents specially
said that the lengths of summer and winter have been changed nowadays compared
to the past. Mean temperature is felt to be increasing in both summer and winter
months in the study area. The length of winter shortened and came late compared
to the past. Almost all the respondents gave some opinion on temperature and
rainfall variations.
Regarding course of disease in the measles like outbreak areas a lot of information
was gathered. In response to reported cases (index case) from Upazila Health
Complex, Sadar Hospital and NGO clinic, a quick investigation performed to
confirm the clinical diagnosis and blood sample collected for serological study. By
tracking index cases (236 cases) in the community a total of 174 measles like
outbreak was identified and confirmed by case investigation and community
searching with a prescribed outbreak investigation format during the study period
(year 2009-2011) within the study area. From each outbreak site 5-10 blood
sample collected for serological study, Immunoglobulin M (IgM) for measles and
Immunoglobulin M (IgM) for rubella to identify the causes of outbreak. On the
basis of laboratory report measles like outbreak were classified as;
90
a) Confirmed measles outbreak- at least 2 sample measles IgM positive;
a) Confirmed rubella outbreak- at least 2 sample rubella IgM positive;
a) Mixed measles rubella outbreak- at least one measles and one rubella
IgM positive; and
a) Discard outbreak- all sample negative for both measles and rubella.
Laboratory report of Measles like outbreak investigation data revealed
(Table-3.6) that out of 174 outbreaks, 11 were laboratory confirmed
measles outbreak consisting of 491 cases, 126 laboratory confirmed
rubella outbreak consisting of 8042 cases, 25 mixed measles and rubella
outbreak consisting of 191 cases and 12 discarded as non-measles non
rubella outbreak consisting of 456 case.
Table-3.6 Measles like Outbreak and Cases in the Study Area
Year
Lab confirmed
Measles
Lab confirmed
Rubella
Mixed measles
& rubella
Discarded
outbreak
No of
OB
No of
case
No of
OB
No of
case
No of
OB
No of
case
No of
OB
No of
case
2009 0 0 55 5338 0 0 4 140
2010 0 0 55 2218 10 97 4 181
2011 11 491 16 586 15 94 4 135
Total 11 491 126 8042 25 191 12 456
NB: OB= Outbreak
A total of 491 measles laboratory positive case were identified during outbreak
searching. The beginning spurt of the outbreak was in the month of January,
gradually increased and peaked at April-May and declined thereafter. Second
episode also found in October and November. There was no single incidence of
measles case in the month of September and December during the study period
(Figure 3.30).
91
Figure-3.30 Presents the Epidemic Curve of Measles Outbreak in the Study
Area during the study period (2009-2011)
The measles outbreak occurred in highly vaccinated population. Out of 491 total
measles patients 309 (59.26%) cases were in between 9 months and 15 years old
(Table-3.7).
Table-3.7 Vaccination status of Lab Confirmed Measles cases in the
Study Area
Age group Case Vaccinated Vaccination coverage
<9 months 12 0 0
9-11 months 17 10 59%
1-4 years 112 112 100%
5-9 years 111 100 90%
10-14 years 69 69 100%
9 months-<15 years 309 291 94%
15-19 years 56 45 80%
20 years 114 11 8%
Total 491 347 70.72%
92
Age distribution (Figure3.31) and sex distribution (Figure 3.32) revealed that
measles disease affected irrespective of sex and ages. The graph showed that 66%
of the measles cases under 15 years age group. 2%, 4%, 23%, 23%, 14% of the
measles cases were >9 months, 9-11 months, 1-4 years, 5-9 years, 10-14 years age
group respectively. Besides this there was 23% patient more than 20 years age.
Figure-3.31 Age distribution of Measles cases in study area
Figure-3.32 Sex Distribution of Measles Cases in the Study Area
93
Post measles complication: A period of one month after the attack of measles was
taken into account for recording post measles complications. Among the 491 Cases
of measles, parents reported one or more post measles complications in 54 cases.
Diarrhoea was the commonest (74%) of all, followed by pneumonia (25%). There
was no death due to measles like outbreak in the study area during the study period
(2009-2011).
Figure-3.33 Comparison of Measles like Outbreak Cases by Lab result in the
study area
Figure 3.33 showed that there was an enormous lab confirmed rubella outbreak
and rubella case in the year 2009 consisting 5238 cases, year 2010 consisting 2218
cases and year 2011 consisting 586 cases. On the contrary there was no lab
confirm outbreak of measles during 2009-2010 but 491 cases lab confirmed
measles cases were diagnosed in 2011.
R
ube
ll
a
Measles
Chapter Four
Discussion
Incidences of infectious diseases in human not only influenced by climatic factors
but also depend on nutritional status, immunization status, socio-economic and
educational status of the individuals, family and community. Under this study
health impacts due to climate change, climate variability issues and their correlation
were assessed by both primary and secondary data/information. The primary data on
family size, socio economic condition, vaccination status of children and the
community perceptions regarding the climatic change and infectious diseases were
generated through face to face interview and cluster survey.
The survey shows that the average household size was 5.1, of which 51.9% male
and 48.1% female population in the study area. Majority 51.4% of the household
members are ranged between 16-60 years age group whereas 18.3% within 5-15
years and 19.6% under 5 years age group. These statistics is consistent with BBS
report 2009.
Though the study shows the knowledge of respondents regarding climate change
was not very satisfactory but most of them have clear cut ideas about the season of
Bangladesh and seasonal association with infectious diseases.
The climate factors like temperature and precipitation were considered as the key
determinants of the distribution of many infectious disease carrying vectors. Water
borne (e.g. diarrhoea, hepatitis A and E), air borne (e.g. ARI, measles, mumps,
rubella) and vector borne (e.g. malaria, kal-azar, dengue) diseases are climate
sensitive. Nipah virus infection, Chikungunia and Japanese encephalitis are
emerging infectious diseases which are also sensitive to weather and climatic
variability (Epstain et. al., 2006 and Hales, 2002).
95
Rising temperature and changing rainfall patterns are expected to have a
substantial effect on the burden of infectious diseases transmitted by insect vectors
and through contaminated water. Insect vectors are generally more active at higher
temperatures, in addition to this there is an increased likelihood of them
establishing themselves in new areas. The greatest effects of climate change on
transmission are likely to be observed at the extremes of the range of temperatures at
which transmission occur (Ranges between 14-18
0
C and 35-40
0
C) (Bradly, 1993).
Bangladesh is vulnerable to outbreaks of waterborne, airborne and vector borne
infectious and other types of diseases (World Bank, 2000). Diseases such as
diarrhoea, dysentery and measles like disease, etc. are also on the rise especially
during the summer months. The medical communities of Bangladesh were fairly
unfamiliar about the presence of dengue in Bangladesh before 2000. Since its
outbreak started in summer of 2000, every year some cases are being reported.
Nipah, Chikungunya fever and Rubella are also re-emerging condition in
previously unaffected areas with possibly changing epidemiology and severity of
the disease. Rubella tends to cluster geographically and overlap with measles
because they share some common features (WHO, SEAR report, 2009).
The present study has revealed changes in the trend of climate factors particularly
yearly and seasonal mean, maximum and minimum temperature and rainfall over
the last three decades in the study area. The long-term changes of temperature of
study area over the period (1964-2011) found to have in general increasing trends
in annual mean and annual mean minimum temperature but the annual mean
maximum temperature slightly declining in recent past decade. Similar results
were also observed by Ara et. al., 2005 and Ferdous et. al., 2011. The long-term
seasonal mean temperatures were also found to have increasing trend. The highest
average maximum temperature 30.55
0
C observed in the month of April in pre
96
monsoon season and lowest average 15.45
0
C in the month of January in winter
season. This observation was also supported by Climate Change Cell (CCC) and
Tawhidul Islam et. al., 2009.
The long-term changes in annual and seasonal rainfall in study area showed
slightly decreasing trend with markedly reduced winter and post monsoon season
rainfall in recent past decade supported by CCC, Bangladesh 2009 report and
Ferdous et. al., 2011. It declined, on average by 3.7mm over Bangladesh and
3.0698 mm/year in Rajshahi region. The present study also confirmed the above
findings that the rainfall in Rajshahi region is on declining state.
The results of the study indicate that the climate factors including temperature and
rainfall (seasonal and annual) are factors for causing infectious disease outbreak
like diarrhea, kala-azar, measles etc. in the study area. This finding is similar to the
study done by CCC, Bangladesh 2009.
In Bangladesh, EPI program has successfully introduced vaccination against 8
vaccine preventable infectious diseases in the aim to reduce childhood morbidity
and mortality. Bangladesh national EPI coverage evaluation survey 2009 stated
BCG coverage 99%, which reflects the universal accessibility of the vaccination
service while measles coverage was 79.4%. However, it is documented that vaccine
efficacy for measles in 85 to 90% (WHO Global Immunization Vision and Strategy:
2006-2015, Bangladesh coverage Evaluation Survey 2009 and Thakur, 2002).
The result of the study showed that the children in the study area were highly
vaccinated with 100 percent accessibility to vaccination schedule and the measles
coverage was 86.20 percent. Among the vaccine preventable diseases only measles
cases and outbreak found in the study area, these indicates vaccine preventable
97
infectious diseases related morbidity and mortality reduced in the study area.
These findings are consistent with Bangladesh Bureau of Statistics report 2009 and
Bangladesh Demographic and Health Survey report 2011. Incidence of measles
like case was found 78 cases in 2009, 54 cases in 2010 and 104 cases in 2011 in
the study area. Tracking the index case a total of 174 measles like outbreak and
were identified and investigated during study period. Measles vaccination status of
9 months to 15 years measles cases was 94.17% indicates that there was primary
vaccination failure occurred and susceptible accumulation causes measles outbreak
in the study area. Primary vaccine failure can be due to inactive vaccine or
inadequate host response. Besides this there was 23% patient more than 20 years
age. which was uncommon in measles epidemiology. It showed that there was a
shift in age group affected towards higher side. Similar observation also supported
by Thakur, 2002, Sydenham, 1979 and London, 1973.
The measles like outbreak investigation data revealed that Rubella is an under
diagnosed emerging infectious disease prevailing in the study area. In addition to
laboratory confirmed measles outbreak a large number of measles like outbreak
identified as laboratory confirm rubella outbreak which is newer in the study area.
Rubella is a mild illness that presents with fever and rash which sometimes
resembles that of measles. Rubella is relatively temperature labile but is more heat
stable than measles virus. The public health importance of rubella is that infection
in the early months of pregnancy usually affects foetal development and produce
congenital rubella syndrome. So the above data indicates that there was large
number of rubella cases in the study area and needs attention for assessing rubella
and congenital rubella syndrome burden in the study area as well as in the country.
98
The correlation coefficients between climate factors and human health disorders
varied. A positive correlation implies that the incidence of diseases increases as
the variation of climatic variables increases. A negative correlation means
decrease in the incidences of diseases when climatic variables level decreases.
Incidence of diarrhoea was found to have positive correlation with total annual and
seasonal rainfall with highest in monsoon (+0.132) and winter (+0.193) rainfalls.
The annual average maximum and minimum temperature was to be found
positively correlated with the incidence of diarrhoea implies that diarrhoea as
endemic in the study area. This finding is consistent with the study done by CCC,
Bangladesh 2009 and ICDDRB published report 2009.
Kala-azar was also found to be positively correlated with rainfall and annual
average maximum temperature (+0.60). However, the correlation was found
negative with annual average minimum temperature. A positive correlation implies
that the incidence of kala-azar increases as the average maximum temperature
increases and negative correlation (-0.635) means decrease in the incidence of
kala-azar when average minimum temperature decreases. The findings are similar
to the study report by CCC, Bangladesh 2009 and Hamida Khannum et. al.,2010.
It was found that most of the kala-azar patients were reported from high and
medium high land barind areas. In contrast, kala-azar was found almost absent in
plane and low land areas in the study districts. Almost all the kala-azar patients
were from low socio-economic condition and living in kacha house. Study also
revealed that the incidence of kala azar in the study area gradually decreases; this
may be due to improve housing, decrease vector population as a result of residual
spraying and improve kala azar case management. This trend coincides with the
trends of kala-azar incidences in Bangladesh over all. Supported by Ramesh, 2010
and Hamida, 2010.
99
The incidence of measles like disease was found positive correlation with
maximum temperature (+0.967) and negatively correlated with average minimum
temperature (-0.003) and total annual rainfalls (-0.475). That is measles like cases
and outbreak found during the highest temperature month of March-May and
declined after heavy rainfall and during winter months. Whereas the measles
epidemics exhibit annual seasonality in which epidemics start in the autumn and
peak in the spring (Fine & Clarkson, 1982, London and Yoke, 1973). This
variation of seasons for measles out breaking might be due to the geographical
location with climatic variation which confirms the positive influence of climatic
changes on infectious diseases.
In addition, climate factors are claimed to be associated with incidence of
emerging Nipah virus infection in the study area. The outbreak of Nipah virus
infection was found during the month of January through May in the study area.
Nipah virus infection after the large outbreak in Malaysia, only three outbreaks
have been reported from other than Bangladesh, one in Singapore and two in India.
Since 2001 Nipah virus infection detected in northwest and central 20 district of
Bangladesh (Chua et. al., 2000-2003 and Homaira et. al., 2007). Therefore, it is
important to know whether specific environmental or host factors are responsible for
recurrent transmission of Nipah virus to humans in specific areas of Bangladesh.
The survey respondents of the study also identified that the climate factors like
temperature, rainfall are sensitive to diarrhea, kala-azar, measles like disease,
jaundice and newer Nipah virus infection and their outbreak among children in the
study area.
100
Conclusions and Recommendations
Based on the findings of this study, the following conclusions are drawn:
1. The long-term changes in temperature of study area over the period (1964-
2011) found to have in general increasing trends in annual mean and annual
mean minimum temperature but the annual mean maximum temperature
slightly declining in recent past decade.
2. The long-term seasonal mean temperatures were also found to have increasing
trend. The highest average maximum temperature 30.55
0
C observed in the
month of April in pre monsoon season and lowest average 15.45
0
C in the
month of January in winter season.
3. The long-term changes in annual and seasonal rainfall in study area showed
slightly decreasing trend with markedly reduced winter and post monsoon
season rainfall in recent past decade.
4. The results of the study indicate that the climate factors including temperature
and rainfall (seasonal and annual) are factors for causing infectious disease
outbreak like diarrhea, kala-azar, measles etc. among children in the study area.
5. The study disclosed that though measles vaccination coverage in the study area
94.17% in 9 months to under 15 years age group nevertheless 309 incidences of
measles cases were confirmed in the laboratory test. It is clear that either the
vaccine was not up to the mark of efficacy or in some cases physiological or
some other factors of the individuals were not synergistic to the vaccine.
101
6. Rubella outbreak is a new phenomenon was identified in the laboratory test,
126 outbreaks during the last three years certainly draw the attention to take
care of it. It has been found that drought and high temperature favors the
multiplication and transmission of the virus. The changing trends of rainfall
and temperature in the study area will inspire rubella outbreak in coming days
if appropriate measures could not be taken.
7. The outbreak of Nipah virus infection was found during the month of January
through May in the study area and climate factors are claimed to be associated
with incidence of emerging Nipah virus infection. However, this aspect needs
further study.
In spite of various limitations and constraints on the data related to climate
variables and infectious disease report in the context of specific location of
Bangladesh, a broad-based and in-depth study should be undertaken for better
understanding of the impacts of climate change on the outbreak of infectious
disease especially among children. The findings from such a study would be
valuable for policy and decision making process relating human health and
sustainable development.
On the basis of the findings of the study gaps in knowledge indicates that future
initiatives are required in the following areas:
Increase in active infectious disease surveillance
• Disease surveillance data are needed to provide a baseline for further broad-
based epidemiological studies. As these data are difficult to gather,
particularly in sub national level, a centralized computer database should be
102
created separately for climate sensitive infectious disease as well as
emerging and re-emerging infectious diseases with full demographic and
epidemiological information.
• Community awareness program on climate change and its impact on health
to build resilience should be held frequently.
Strengthen of routine Immunization programme
• Policy adopted to find out left out and drop out cases and to be vaccinated
within scheduled time.
• Introduction of new vaccine to protect the children from vaccine
preventable infectious diseases as like as rubella and others.
• In all cases purity and efficacy as well as compatible doses shall have to be
ensured for fruitful outcome.
Improvements in public health infrastructure
• These includes training of health professionals on climate change and its
impact on infectious diseases as well as human health, training on
emergency response, and prevention and control programmes and increase
awareness programmes among general people to deal with future adversity.
• The epilogue is that for ensuring public health constant keen observation,
analyzing the changing climatic conditions, building up public awareness
about the infectious diseases, early identification and routine checkup of the
patients, and appropriate vaccination after proper investigation by well-
equipped and well trained physician and personnel are the prerequisites and
indispensible. It seems that all the recommendations made above may be
executed successfully only by the sincere cooperation of nationally and
globally concerned authorities.
103
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