ArticlePDF Available
Journal of US-China Medical Science 14 (2017) 116-122
doi: 10.17265/1548-6648/2017.03.003
Modeling of HIV Transmission in Nasarawa State,
Nigeria: An Analysis of Distribution of New Infections
Ishaku Ara Bako1, Abdulsamad Salihu2, Ifeanyi Okekearu2 and Jennifer Anyanti2
1. Department of Epidemiology and Community Health, College of Health Sciences, Benue State University, Makurdi, Benue State,
Nigeria
2. Society for Family Health (SFH), Abuja, FCT 970101, Nigeria
Abstract: The need to understand local HIV epidemics and linking the prevention and other interventions to evidences become very
important for the success of HIV response. The objective of the study was to estimate the distribution of new HIV infections among
adult population (15-49 yrs) and to identify the groups at highest risk of HIV infection in Nasarawa State Nigeria to inform HIV
prevention programme planning and Implementation. The study was based on the Modes of HIV Transmission (MOT) incidence model
recommended by the Joint United Nation’s Programme on AIDS (UNAIDS). Persons aged 15-49 years were divided into independent
groups based on their risky behaviours. Demographic, epidemiological and behavioral data were obtained for each risk group from
available survey reports/documents and inputed into the UNAID’s MOT Model spreadsheet.The model estimated that more than 45%
of new infections would occur amongst persons who reported low risk sex. The Injecting Drug Users, Female Sex Workers (FSW)
and Men having Sex with Men and their partners were estimated to contribute 20.7%. Persons reporting low risk sex practices, a
sub-population that includes cohabiting or married sexual partners need to be targeted with appropriate HIV prevention interventions
such as HIV Counselling and Testing, condom promotion, Interpersonal communications and other partner reduction strategies.
Key words: Risk group, incidence, modes of transmission.
1. Introduction
The HIV/AIDS epidemic is now in its 3rd decade
with an estimated 34 million people living with HIV
worldwide at the end of 2011. Sixty percent of all
people living with HIV reside in sub-Saharan Africa.
Nigeria has the second largest population of persons
living with HIV in the World with an estimated 3.1
million living with the disease [1]. Nasarawa state is
one of the states with high HIV/AIDS prevalence in
Nigeria. Estimates from Nigeria’s antenatal clinic HIV
sentinel survey shows the state has HIV prevalence of
7.5% compared to the national average of 4.1% [2].
One of the factors fuelling the epidemic in Nasarawa
state its proximity to Abuja, Nigeria’s federal capital.
This results to the influx of migrant populations into
the state.
Corresponding author: Ishaku Ara Bako (MBBS, FMCPH),
senior lecturer, research fields: epidemiology, medical statistics,
health services management.
HIV prevention interventions need to be targeted at
populations that are experiencing the highest burden of
new (incident) infections. The Joint United Nation’s
Programme on AIDS’ (UNAIDS) Modes of
Transmission (MOT) model uses national prevalence
and behavioural data to model the distribution of
incidence in key risk populations. It is an important
tool in supporting country and sub-national teams to
understand their epidemics to enable them make better
decisions on prioritization and definition of goals and
targets for effective scale up to Universal Access [3].
The UNAIDS in collaboration with the World Bank in
2007 assisted some countries in East and Southern
Africa to successfully apply the Incidence by Modes of
Transmission Model [4-6]. This was followed by
analysis in West African countries including Nigeria in
2008 [7-10]. Reports have indicated that substantial
heterogeneity exists within a country necessitating that
local data on HIV epidemic be used to inform local
D
DAVID PUBLISHING
Modeling of HIV Transmission in Nasarawa State, Nigeria: An Analysis of Distribution of New Infections
117
HIV interventions [11]. However, there is lack of
information on HIV incidence to inform HIV and
AIDS prevention interventions [12-14].
The Modes of HIV analysis in Nasarawa State was
an attempt to apply the UNAIDS’ model to define the
pattern of new HIV infection at a sub national level. It
was aimed at understanding the local epidemic in
Nasarawa State using available HIV prevalence,
demographic and behavioural data and thus to improve
the scope, relevance and comprehensiveness of the
state HIV prevention efforts. Specifically, the
Modes of Transmission review was to identify the
distribution of the most recent infections and the
populations at greatest risk for infection through
incidence modelling and to make recommendations for
prevention, policy and programmatic actions to ensure
a stronger and more effective state level prevention
strategy.
2. Materials and Methods
The project was conducted by a state team,
supported by the Department for International
Development-funded Enhancing Nigeria’s Response to
HIV and AAIDS Programme (DFID/ENR) programme
with guidance from an MOT modelling consultant.
2.1 Modes of Transmission Model
The purpose of the model was to calculate the
expected short-term (one year) incidence of HIV
infections among the adult population by mode of
transmission. The calculation was based on the current
prevalence of HIV infection, the number of individuals
in particular risk groups, and the risk of exposure to
infection within each group. The model utilized a
spreadsheet based on the UNAIDS Reference Group
on Estimates, Modelling and Projections [15].
Key documents that provided inputs for the model
include the following: 2005 and 2008 Antenatal Care
Serological Surveillance Surveys, the Nigerian
Demography and Health Survey (NDHS) 2008, the
Nigerian HIV/AIDS and Reproductive Health Survey
(NARHS) 2003 and 2005, the National Behavioural
Surveillance Survey (BSS) 2005, the country’s first
Integrated Bio-Behavioural Surveillance Survey
(IBBSS) 2007 and the country’s first population based
HIV sero-prevalence surveillance survey (NARHS
plus 2007). Where Nasarawa State representative data
did not exist, North Central geopolitical zonal values
were used or results of surveys that included proximal
states. Where no zonal or proximal data were not
available, reliable in-country research findings were
used.
These values were then shared with stakeholders
within the State through a stakeholders’ workshop and
externally through correspondence for input and
consensus. These inputs were used to finalise the
model.
2.2 Inputs
2.2.1 Percentage of Population with Risk Behaviour
The adult (15-49 years) population in Nasarawa was
divided into groups based on their highest risk factor
from the main transmission modes in the country:
sexual transmission (heterosexual and homosexual)
and sharing needles during intravenous drug use.
Initially the general adult (15-49 years) population,
disaggregated by sex, was differentiated by their sexual
activity over the last 12 months. Based on data from the
NDHS 2008, and NARHS plus 2007, they were
divided into those that did not have sex in the last 12
months; those that had sex but with only marital partner
and those that had non-marital sex. For this assessment,
the definition of commercial sex was agreed to be the
“exchange of gifts or money for sex”.
The percentage of men who have sex with men
(MSM) was determined from the high-risk group
surveys (IBBSS 2007) conducted in the country. The
fraction of persons that reported injecting drug use was
determined from the general population behavioural
survey (NARHS 2003).
2.2.2 Sexual Partners of Persons within High Risk
Groups
Modeling of HIV Transmission in Nasarawa State, Nigeria: An Analysis of Distribution of New Infections
118
The MOT model aims to show the effect of risk not
only from the perspective of the person who has sex or
other risk behaviours associated with HIV infection,
but also the effect of their behaviours on their sexual
partners.
(1) Sexual partners of male injecting drug users: To
estimate the percentage of females who were stable
partners of IDUs, the percentage of IDUs who reported
living with their sexual partners, independently of
whether they were married or not, was multiplied by
the percentage of the male population who were IDUs:
this was equal to 0.25 * 0.4 = 0.10%. This information
was taken from the IBBSS 2007.
(2) Sexual partners of female injecting drug users:
Unfortunately, the IBBSS did not provide reliable
information on female IDUs’ sexual characteristics.
We were more interested in regular sexual partners of
female IDUs. We made an approximation, that 70.6%
of female partners of IDU were either married or living
with their partners. This was because in the NHDS
2008, this percentage of women was reported to be in
marital or cohabiting union.
(3) Sexual partners of MSM: This was obtained from
percentage of MSM were married or living with
partners.
(4) Sexual partners of clients of Female sex workers:
Partners of clients of sex workers were estimated from
the percentage of clients of sex worker who were
married according to the NDHS. These partners of
FSW clients were hitherto assumed to have been low
risk.
(5) Sexual partners of men and women engaging
casual heterosexual sex: To estimate the number of
persons who were engaging in casual sex we assumed
the default values in the model i.e. that 80% of persons
engaging in casual sex had a regular partner.
2.3 HIV Prevalence
Prevalence amongst the general population was
based on the 2007 NARHS plus population based
sero-prevalence survey conducted in the country.
Nasarawa state had a prevalence of 6.8%. The
prevalence amongst the high-risk groups was based on
the 2007 Integrated Behavioural and Biological survey
conducted amongst High Risk groups in Nigeria. The
prevalence amongst partners of high-risk groups
(partners of FSWs) was estimated by studying the
relationship between sexual behaviour and HIV
prevalence in West African countries and limited
research in Nigeria and deducing the possible
prevalence amongst these groups based on the
prevalence amongst the general population and the
high risk groups.
2.4 STI Prevalence
Sexually Transmitted Infections (STIs) are known to
affect the rate of transmission of HIV during sex. The
prevalence of STI in the population and its distribution
amongst the various groups will affect the rate of HIV
transmission through sex. The prevalence of infection
was estimated by the percentage of the various groups
that reported having unusual genital discharge or a
genital ulcer in the last 12 months. The percentage for
the general population was obtained from the 2008
NDHS while the percentages for the high-risk groups
were obtained from the IBBSS 2007.
2.5 Number of Sexual Partners and Acts per Partner
per Year
An assumption was made that the average sexually
active person had about 100 acts of sexual intercourse a
year as in the latest NDHS surveys where this question
was asked the reported number varied between 50 and
100 sex acts per year.
According to the IBBSS 2007, brothel based FSW
and non-brothel based FSW had on average 34 and 25
clients per week respectively. As the sample, sizes of
these two groups were quite close it was assumed that
each represented half of the FSW population and it was
estimated that FSW had an average of 2 clients per day
for 20 days. Assuming, FSW take 12 weeks off due to
menstrual periods. Their total number of clients per
Modeling of HIV Transmission in Nasarawa State, Nigeria: An Analysis of Distribution of New Infections
119
year was: 600.
The number of sex partners per year was calculated
by determining the average number of partners that
people in each group had based on their responses to
questions in the various surveys conducted in the
country. People reporting no sexual activity in the last
12 months were presumed to have no sexual partner;
those reporting only marital sex were presumed to have
only one sexual partner and those stating that they had
had non-marital sex were assumed to have more than
one.
2.6 Percentage of Acts Protected (%)
These are the number of sex acts in which the
persons took precaution against HIV infection by using
a condom; this is approximated by determining the
percentage of last acts of sex in which a condom was
used. These were obtained from the IBBSS and the
NDHS 2003 & NARHS 2005. Condom use among
persons in the low risk group was presumed to be the
same for the state as the current use of condoms
reported in the NARHS+ 2007 for North Central zone.
3. Results
The model estimated that 3,335 new infections
would occur in the following one year amongst the
15-49 years adult population (Table 1).
The exposure groups with the highest incidence risk
were persons who reported low risk sex in the previous
year. They were estimated to account for about 47% of
all new infections. About 23% of infections would
occur amongst people who are sexual partners of
high-risk groups (female sex partners of MSM;
partners of IDUs, partners of clients of female sex
workers and partners of persons who have casual
high-risk sex (Table 1, Fig. 1).
Directly, IDU, FSW and MSM with their partners,
contribute as much as 21% of new infections. New
infections arising from commercial (transactional) sex
accounted for 8% of new cases, of which of clients
dominated with 4.9% of all new cases.
Persons who had casual sex and their partners
accounted for about 32% (9.8% and 21.8%
respectively) of new infections. Medical injections and
blood transfusion together accounted 0.9% (0.32% and
0.61% respectively) (Fig. 1).
Table 1 Incidence of HIV infections in one year among adults in Nasarawa Nigeria, 2010.
Adult risk category
Total number with risk behaviour
Incidence
% of incidence
Injecting Drug Use (IDU)
1,303
201
6.04
Partners IDU
600
6
0.17
Sex workers
4,344
61
1.82
Clients
16,508
164
4.92
Partners of Clients
5,613
42
1.26
MSM
3,041
205
6.13
Female partners of MSM
1,186
13
0.39
Casual heterosexual sex
152,919
328
9.83
Partners CHS
122,335
727
21.79
Low-risk heterosexual
318,598
1,558
46.71
No risk
242,412
0
0.00
Medical injections
868,860
11
0.32
Blood transfusions
8,689
20
0.61
Estimated total adult population
868,860
3,335
100.00
Modeling of HIV Transmission in Nasarawa State, Nigeria: An Analysis of Distribution of New Infections
120
Fig. 1 Estimated Proportion of New HIV Infection among adult risk groups population in Nasarawa State Nigeria, 2010.
4. Discussion
More than 45% of the infections occur amongst
persons practicing low risk sex. This finding is
higher than what was found from other countries and
National estimates from Nigeria. In the West African
sub region, about 30% of all new infections occur in
people who have low risk behaviour. It was estimated
to be 36% for Nigeria, 28% (Benin), 28% (Ghana), and
24% in Côte d'Ivoire [15], 44.1% (Kenya) [16], 56%
(Iran) [17]. This could be accounted for by among other
reasons low HCT rate; only 36.1% of men and 34.1%
of women in the state ever tested for HIV [18]. HIV
infection acquired because of previous or present
high-risk behaviours or relationships by one of the sex
partners is easily transmitted to unsuspecting partners.
The presumed perceived low risk of infection amongst
persons who themselves are keeping to one partner
faithfully, needs to be addressed. The notion that one is
safe because he or she is doing the right thing needs to
be revised to educate people that they are not safe until
their partners are also faithful. There is a need to ensure
that people are aware of the HIV status and the sexual
practices of their partners. Any form of doubt needs to
be addressed through the use of condoms during sex.
About 24% of new HIV infections were estimated to
occur amongst people who are sexual partners of
high-risk groups (female sex partners of MSM;
partners of IDUs, partners of clients of female sex
workers and partners of persons who have casual
high-risk sex). This finding did not agree with a
previous study which showed that in North Africa and
Middle East, Sex workers and IDUs contribute the
highest proportion of new HIV infection [19]. In Kenya,
6.04
0.17
1.82
4.92
1.26
6.13
0.39
9.83
21.79
46.71
0
0.32
0.61
0 10 20 30 40 50
Injecting Drug Use (IDU)
Partners IDU
Sex workers
Clients
Partners of Clients
MSM
Female partners of MSM
Casual heterosexual sex
Partners CHS
Low-risk heterosexual
No risk
Medical injections
Blood transfusions
Modeling of HIV Transmission in Nasarawa State, Nigeria: An Analysis of Distribution of New Infections
121
sex workers and their clients, IDUs, MSM and prison
population contribute 33% of new infections [20].
Partners of CHS, IDUs and of FSWs’ clients are people
who ordinarily should have been classified as low risk
but are now at a higher risk of acquiring HIV infection
because of their relationships with people known to
practice high risk sex and therefore not very visible as
high-risk groups.
In spite of the fact that the majority of the infections
were due to the HIV transmission amongst the general
population, the high-risk groups still contribute a
significant portion of the new HIV infections. Directly,
IDU, FSW and MSM with their partners, contribute as
much as 21% of new infections. This is quite
significant because these groups constitute only about
3% of the adult population.
The modeling exercise in Nasarawa State has
brought out a number of limitations in the application
of the UNAIDS Model particularly at a sub-national
level. The Model does not take into account the
heterogeneity in risk behaviours within each risk group
as individuals were placed in groups considered to be
the highest risk. However, effect of multiple exposures
in same individuals on HIV transmission probability
may be higher than effect of the highest risk alone. In
addition, there was limited state specific data at the
time of the modeling necessitating the use data from
contiguous states or zonal averages which may not be
exactly true for the state. As new data become available
and because the pattern of HIV transmission changes
over time [14], it is imperative that MoT analysis is
repeated on a regular basis. Finally, the analysis used
findings from surveys which relied on self reported
behaviours with possibilities of bias. However, the
exercise provided an opportunity to build the capacity
of stakeholders from the state on MOT analysis and as
more data become available, subsequent exercise
would be conducted with minimal support from outside
the state. The findings from this study could also be
used as an advocacy tool to government and donors to
solicit for appropriate funding for the state HIV
prevention interventions.
HIV Counselling and Testing (HCT) needs to be
scaled up rapidly to the general population in the state.
Efforts must be made to get couples to undergo couple
HCT. Condom use should be socially marketed to be
the norm in any sexual relationship especially where
the partners dont know their HIV status. There is need
to overcome all barriers to condom usage including
socio-cultural factors and poor availability.
Opportunities for mass campaign and social movement
should be explored with religious and community
leaders to discourage multiple partnering as a threat to
individual and public health. Community based HIV
prevention interventions such as Interpersonal
Communications (IPC), Society Tackling AIDS
through Rights (STAR), Peer Education Plus (PEP)
model, Priority for Local AIDS Control Efforts
(PLACE) and Voice For Humanity (VFH) which has
already been piloted in the state should be scaled up
rapidly to increase HIV knowledge and effect
appropriate behavioural change among the general
population. Budgeting for HIV Prevention should take
distribution of new infections into consideration and
based on the relative magnitude of the mode of
transmission. There is need to carry out state specific
surveys to estimate the size and characteristics of
injecting drug users, men having sex with men and
their partners as well as clients of sex workers to use for
future MOT analysis. National HIV related biological
and behaviours surveys should be disaggregated by
state to enable findings to be more useful at the state
level.
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Analyses of HIV incidence in Nasarawa State Nigeria estimate that most of the new HIV infections occur among persons who reported low HIV risk including couples. The study was aimed at identifying the factors that predict risky sexual behavior among the general population in Nasarawa state, Nigeria. Data analysis was carried on a total of 801 respondents sampled from the general population of Nasarawa State, Nigeria. The original sample was obtained through a two-stage cluster sampling technique using probability proportionate to size. The primary outcome variable was risky sexual behavior. Chi-square and logistic regression analyses were used to determine the association between the outcome and selected Sociodemographic and other independent variables. Females were 54.2% of the total sampled population analysed, the mean age of the respondents was 29.8 years (SD: 10.3). About two-third of the respondents engaged in risky sexual behaviours (65.9%) but only 4.7% considered themselves to be at high risk of HIV. The multivariable regression analysis showed that factors associated with risky sexual behaviour included : been male sex [OR: 0.63; 95% CI: 0.436-0.915], married [OR: 0.26: 95% CI: 0.163 - 0.419], rural resident [OR: 1.20; 95% CI: 0.775 to 1.871 ], age 20-24 [OR: 1.93, 95% CI: 1.113 - 3.360] and 25-29 years [OR: 2.34; 95% CI: 1.267-1.308]; and knowledge of HIV [OR: 1.49; 95% CI: 1.056-2.108].There is a need to urgently intensify media campaigns, community-based interventions including one on one communications to reduce risky sexual behaviours.
... This is in line with findings from the analyses of new HIV infections in Nasarawa State Nigeria which revealed that close to half of all new HIV infections in the state occur among persons who reported low risk including married partners. 6 The male partners often serve as the bridge between the traditional high risk populations such as sex workers, MSM and injecting drug users and the general population. ...
Article
Full-text available
Analyses of HIV incidence in Nasarawa State Nigeria estimate that most of the new HIV infections occur among persons who reported low HIV risk including couples. The study was aimed at identifying the factors that predict risky sexual behavior among the general population in Nasarawa state, Nigeria. Data analysis was carried on a total of 801 respondents sampled from the general population of Nasarawa State, Nigeria. The original sample was obtained through a two-stage cluster sampling technique using probability proportionate to size. The primary outcome variable was risky sexual behavior. Chi-square and logistic regression analyses were used to determine the association between the outcome and selected Sociodemographic and other independent variables. Females were 54.2% of the total sampled population analysed, the mean age of the respondents was 29.8 years (SD: 10.3). About two-third of the respondents engaged in risky sexual behaviours (65.9%) but only 4.7% considered themselves to be at high risk of HIV. The multivariable regression analysis showed that factors associated with risky sexual behaviour included : been male sex [OR: 0.63; 95% CI: 0.436-0.915], married [OR: 0.26: 95% CI: 0.163 - 0.419], rural resident [OR: 1.20; 95% CI: 0.775 to 1.871 ], age 20-24 [OR: 1.93, 95% CI: 1.113 - 3.360] and 25-29 years [OR: 2.34; 95% CI: 1.267-1.308]; and knowledge of HIV [OR: 1.49; 95% CI: 1.056-2.108].There is a need to urgently intensify media campaigns, community-based interventions including one on one communications to reduce risky sexual behaviours.
... This is in line with findings from the analyses of new HIV infections in Nasarawa State Nigeria which revealed that close to half of all new HIV infections in the state occur among persons who reported low risk including married partners. 6 The male partners often serve as the bridge between the traditional high risk populations such as sex workers, MSM and injecting drug users and the general population. ...
Article
Analyses of HIV incidence in Nasarawa State Nigeria estimate that most of the new HIV infections occur among persons who reported low HIV risk including couples. The study was aimed at identifying the factors that predict risky sexual behavior among the general population in Nasarawa state, Nigeria. Data analysis was carried on a total of 801 respondents sampled from the general population of Nasarawa State, Nigeria. The original sample was obtained through a two-stage cluster sampling technique using probability proportionate to size. The primary outcome variable was risky sexual behavior. Chi-square and logistic regression analyses were used to determine the association between the outcome and selected Sociodemographic and other independent variables. Females were 54.2% of the total sampled population analysed, the mean age of the respondents was 29.8 years (SD: 10.3). About two-third of the respondents engaged in risky sexual behaviours (65.9%) but only 4.7% considered themselves to be at high risk of HIV. The multivariable regression analysis showed that factors associated with risky sexual behaviour included : been male sex [OR: 0.63; 95% CI: 0.436-0.915], married [OR: 0.26: 95% CI: 0.163-0.419], rural resident [OR: 1.20; 95% CI: 0.775 to 1.871 ], age 20-24 [OR: 1.93, 95% CI: 1.113-3.360] and 25-29 years [OR: 2.34; 95% CI: 1.267-1.308]; and knowledge of HIV [OR: 1.49; 95% CI: 1.056-2.108].There is a need to urgently intensify media campaigns, community-based interventions including one on one communications to reduce risky sexual behaviours.
Article
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Objective An increasing number of countries have been estimating the distribution of new adult HIV infections by modes of transmission (MOT) to help prioritise prevention efforts. We compare results from studies conducted between 2008 and 2012 and discuss their use for planning and responding to the HIV epidemic. Methods The UNAIDS recommended MOT model helps countries to estimate the proportion of new HIV infections that occur through key transmission modes including sex work, injecting drug use (IDU), men having sex with men (MSM), multiple sexual partnerships, stable relationships and medical interventions. The model typically forms part of a country-led process that includes a comprehensive review of epidemiological data. Recent revisions to the model are described. Results Modelling results from 25 countries show large variation between and within regions. In sub-Saharan Africa, new infections occur largely in the general heterosexual population because of multiple partnerships or in stable discordant relationships, while sex work contributes significantly to new infections in West Africa. IDU and sex work are the main contributors to new infections in the Middle East and North Africa, with MSM the main contributor in Latin America. Patterns vary substantially between countries in Eastern Europe and Asia in terms of the relative contribution of sex work, MSM, IDU and spousal transmission. Conclusions The MOT modelling results, comprehensive review and critical assessment of data in a country can contribute to a more strategically focused HIV response. To strengthen this type of research, improved epidemiological and behavioural data by risk population are needed.
Article
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Introduction The HIV Modes of Transmission (MOT) model estimates the annual fraction of new HIV infections (FNI) acquired by different risk groups. It was designed to guide country-specific HIV prevention policies. To determine if the MOT produced context-specific recommendations, we analyzed MOT results by region and epidemic type, and explored the factors (e.g. data used to estimate parameter inputs, adherence to guidelines) influencing the differences. Methods We systematically searched MEDLINE, EMBASE and UNAIDS reports, and contacted UNAIDS country directors for published MOT results from MOT inception (2003) to 25 September 2012. Results We retrieved four journal articles and 20 UNAIDS reports covering 29 countries. In 13 countries, the largest FNI (range 26 to 63%) was acquired by the low-risk group and increased with low-risk population size. The FNI among female sex workers (FSWs) remained low (median 1.3%, range 0.04 to 14.4%), with little variability by region and epidemic type despite variability in sexual behaviour. In India and Thailand, where FSWs play an important role in transmission, the FNI among FSWs was 2 and 4%, respectively. In contrast, the FNI among men who have sex with men (MSM) varied across regions (range 0.1 to 89%) and increased with MSM population size. The FNI among people who inject drugs (PWID, range 0 to 82%) was largest in early-phase epidemics with low overall HIV prevalence. Most MOT studies were conducted and reported as per guidelines but data quality remains an issue. Conclusions Although countries are generally performing the MOT as per guidelines, there is little variation in the FNI (except among MSM and PWID) by region and epidemic type. Homogeneity in MOT FNI for FSWs, clients and low-risk groups may limit the utility of MOT for guiding country-specific interventions in heterosexual HIV epidemics.
Article
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The modes of transmission model has been widely used to help decision-makers target measures for preventing human immunodeficiency virus (HIV) infection. The model estimates the number of new HIV infections that will be acquired over the ensuing year by individuals in identified risk groups in a given population using data on the size of the groups, the aggregate risk behaviour in each group, the current prevalence of HIV infection among the sexual or injecting drug partners of individuals in each group, and the probability of HIV transmission associated with different risk behaviours. The strength of the model is its simplicity, which enables data from a variety of sources to be synthesized, resulting in better characterization of HIV epidemics in some settings. However, concerns have been raised about the assumptions underlying the model structure, about limitations in the data available for deriving input parameters and about interpretation and communication of the model results. The aim of this review was to improve the use of the model by reassessing its paradigm, structure and data requirements. We identified key questions to be asked when conducting an analysis and when interpreting the model results and make recommendations for strengthening the model's application in the future.
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Despite worldwide efforts to prevent HIV infection, the number of people affected continues to rise. The authors of this article argue that a commonsense approach based on simple country by country analyses could improve the situation.
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Patterns of transmission of HIV are different among different regions of the world and change over time within regions. In order to adapt prevention strategies to changing patterns of risk, we need to understand the behaviours that put people at risk of infection and how new infections are distributed among risk groups. A model is described to calculate the expected incidence of HIV infections in the adult population by mode of exposure using the current distribution of prevalent infections and the patterns of risk within different populations. For illustration the model is applied to Thailand and Kenya. New infections in Kenya were mainly transmitted through heterosexual contact (90%), while a small but significant number were related to injecting drug use (4.8%) and men who have sex with men (4.5%). In Thailand, the epidemic has spread over time to the sexual partners of vulnerable groups and in 2005 the majority of new infections occurred among the low risk heterosexual population (43%). Men having sex with men accounted for 21% and sex work (including sex workers, clients, and partners of clients) for 18% of new infections. Medical interventions did not contribute significantly to new infections in either Kenya or Thailand. The model provides a simple tool to inform the planning of effective, appropriately targeted, country specific intervention programmes. However, better surveillance systems are needed in countries to obtain more reliable biological and behavioural data in order to improve the estimates of incidence by risk group.
Technical report 2010: National HIV/Syphilis sero-prevalence sentinel survey among pregnant women attending antenatal clinics in Nigeria
Federal Ministry of Health, Department of Public Health, National AIDS/STI Control Programme. 2010. Technical report 2010: National HIV/Syphilis sero-prevalence sentinel survey among pregnant women attending antenatal clinics in Nigeria. Abuja.
Kenya: HIV Prevention Response and Modes of Transmission Analysis Report
  • L Gelmon
  • P Kenya
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Gelmon, L., Kenya, P., Oguya, F., Cheluget, B., and Haile, G. 2009. Kenya: HIV Prevention Response and Modes of Transmission Analysis Report. Kenya National AIDS Control Council, UNAIDS, World Bank Global HIV/AIDS Program/Global AIDS M&E Team.
Lesotho: Analysis of Prevention Response and Modes of Transmission Study
  • M Khobotlo
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  • A Chitoshia
  • M Hildebrand
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Khobotlo, M., Teshelo, R., Nkonyana, J., Ramoseme, M., Khobotle, M., Chitoshia, A., Hildebrand, M., and Fraser, N. 2009. Lesotho: Analysis of Prevention Response and Modes of Transmission Study, Kingdom of Lesotho, UNAIDS, World Bank Global HIV/AIDS Program Report.
Uganda: HIV Modes of Transmission and Prevention Response Analysis Report
  • F Wabwire-Mangen
  • M Odiit
  • W Kirungi
  • D Kawaeesa Kisitu
  • Okara Wanyama
Wabwire-Mangen, F., Odiit, M., Kirungi, W., Kawaeesa Kisitu, D., and Okara Wanyama, J. 2009. Uganda: HIV Modes of Transmission and Prevention Response Analysis Report, Uganda AIDS Commission, UNAIDS.