The public health impact of tsunami disasters

Abstract

Tsunamis have the potential to cause an enormous impact on the health of millions of people. During the last half of the twentieth century, more people were killed by tsunamis than by earthquakes. Most recently, a major emergency response operation has been underway in northeast Japan following a devastating tsunami triggered by the biggest earthquake on record in Japan. This natural disaster has been described as the most expensive in world history. There are few resources in the public health literature that describe the characteristics and epidemiology of tsunami-related disasters, as a whole. This article reviews the phenomenology and impact of tsunamis as a significant public health hazard.

Full text

Abstract
Tsunamis have the potential to cause an enormous
impact on the health of millions of people. During the
last half of the twentieth century, more people were
killed by tsunamis than by earthquakes.1Most recently,
a major emergency response operation has been under-
way in northeast Japan following a devastating
tsunami triggered by the biggest earthquake on record
in Japan. This natural disaster has been described as
the most expensive in world history.2There are few
resources in the public health literature that describe
the characteristics and epidemiology of tsunami-
related disasters, as a whole. This article reviews the
phenomenology and impact of tsunamis as a signifi-
cant public health hazard.
Key words: tsunami, natural disasters, public
health emergency, disasters
Purpose
Tsunamis are a recurring natural phenomenon
with far-reaching and devastating impacts. Public
health and medical impacts are often overwhelmed by
the adverse effects of tsunami disasters on both the
health of the population and health infrastructure. An
understanding of the tsunami phenomenon itself as
well as its public health impacts may serve to advise
population at risk on how best to reduce their own vul-
nerabilities. The purpose of this manuscript is to
review the origins and physics of tsunamis, history of
several tsunamis, factors contributing to the tsunami
effects, and overview on the public health impacts of
tsunamis.
Background nature of tsunamis
Definition
The Japanese word tsunami translates in English
to “harbor wave.”
A tsunami is a series of ocean waves generated by
any disturbance that displaces a large water mass.3
About 90-95 percent of tsunamis are caused by large
earthquakes (usually Richter magnitude 6.5 or greater);
the remainders are primarily due to volcanic eruptions
(like the eruption of Mt Krakatau in 1883) or landslides
(like the 1998 Papua New Guinea tsunami generated by
a submarine landslide). There are also composite events
such as the 1946 subduction earthquake in the Aleutian
Islands that triggered a landslide-generated tsunami
killing 159 in Hawaii.4Prehistoric geological evidence
has also implicated meteorites or comet impacts as a
rare cause of tsunami (the most notable is located near
the Yucatán Peninsula in the Gulf of Mexico).5
To understand tsunamis, it is helpful to distinguish
them from wind-generated waves or tides.Wind blow-
ing across the ocean deforms the surface into relatively
short waves to create currents restricted to a shallow
surface layer. Strong gales are able to whip up waves
100 ft (30 m) or higher in the open ocean but even these
do not move deep water.6Wind-generated surface
waves typically have a high frequency and short wave-
length (distance between wave crests) when compared
with the extremely low frequency and long wavelength
of tsunami waves.Tsunamis often are called by the pop-
ular name, “tidal waves,” but this is a misnomer. They
are not caused by tidal action of the moon and sun like
www.disastermedicinejournal.com 34 1
The public health impact of tsunami disasters
Mark E. Keim, MD
ORIGINAL ARTICLE
DOI:10.5055/ajdm.2011.0073
DM

the regular ocean tides. Rather they are long water
waves generated by sudden displacement of the earth
under water.
Causes of tsunamis
The type of earthquake is as important as its
strength in determining whether a tsunami will occur
or not. The earth’s crust is made up of a “jigsaw puzzle”
of tectonic plates that abut and move against each
other. Subduction zones are faults in the earth’s crust in
which one tectonic plate overrides another. Movement
along this type of fault typically produces the vertical
land movement necessary to generate a tsunami.
Subduction earthquakes can impart a vertical displace-
ment in the earth’s surface that is hundreds of miles
long and thus displace billions of tons of water.
Earthquakes that produce largely horizontal move-
ment (ie, the San Andreas Fault in California) do not
typically generate tsunamis. In addition, the causative
earthquake must occur at relatively shallow (<31 miles
or 50 km) depths underground to efficiently transfer
ground energy to the water above. Great transocean
tsunamis are typically caused by massive subduction
earthquakes whose rupture zones extend several hun-
dreds of kilometers along the trench. These earth-
quake-generated tsunamis spread outward in all
directions from the point of origin.7In comparison,
tsunamis triggered by submarine landslides produce a
relatively narrow radiation pattern resulting in a
focused beam of energy with the potential of also reach-
ing far afield.4
Giant submarine landslides (and impacts from
extraterrestrial sources such as comets and meteors)
have the potential to create extremely large waves
referred to as megatsunamis. At least 100 megat-
sunamis in different parts of the world have been
recorded in the past 2,000 years according to interpre-
tation of the sedimentologic and geomorphic imprints
left by these events.8Megatsunamis produced by giant
submarine landslides were first proposed for Hawaii
and have since been implicated globally on other
oceanic islands along with continental margins.9For
instance, marine deposits in the Hawaiian Islands
that lie up to 1,230 ft (375 m) above sea level on the
island of Lanai have been attributed to the action of a
megatsunami generated by giant submarine land-
slides from Mauna Loa volcano on the big island of
Hawaii.10 Giant wave deposits found in the Bahamas
coincide with a prehistoric volcano collapse in La
Palma, Canary Islands.11
The physics of tsunami phenomenon
Regardless of their origin, tsunamis evolve through
the three overlapping but quite distinct physical
processes: “generation” by any force that disturbs the
water column, “propagation” from deeper water near
the source to shallow coastal areas, and, finally, “inun-
dation” of dry land.
Generation is the process by which a seafloor dis-
turbance, such as movement along a fault, reshapes
the sea surface into a tsunami. Vertical displacement of
the ocean floor results in a transfer of seismic energy to
the entire column of water above. Propagation of the
tsunami transports seismic energy away from the
earthquake site through the water just as shaking
moves the energy through the earth during an earth-
quake. Once the tsunami is generated, a series of
extremely low frequency, long wavelength (~186 miles
or 300 km) waves are propagated in an expanding
radius from the area of displacement traveling at a
speed proportional to the square root of the depth of
water reaching up to 600 miles/h (965 km/h) in the
deep ocean.
Because the energy is spread throughout such a
large volume in deep water and have such a long wave-
length between crests, tsunamis may be only a few feet
(<1 m), high in mid-ocean, making them capable of
passing under oceangoing ships with little disturbance
or detection. The physical dynamics of the fluid pres-
sure wave allows it to travel great distances with very
little loss of energy. For example, a subduction earth-
quake occurring on January 26, 1700 at the Cascadia
subduction zone encompassing western Washington
and Oregon generated a tsunami that destroyed the
island of Honshu, Japan.12,13
The dependence of wave speed on water depth also
causes individual waves to slow down as they
approach shallow water, so they begin to overtake one
another decreasing the distance between them in a
process called shoaling. Refraction of the wave off the
American Journal of Disaster Medicine
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34 2

seafloor and shoaling focuses the same amount of
energy into a smaller volume of water creating higher
waves and faster currents as the tsunami reaches
land.6
The last stage is inundation in which a tsunami
may run ashore as a breaking wave, a wall of water or
a tide-like flood is perhaps the most difficult to model.
Vertical run-up typically takes only 2-3 m to cause
damage along the shoreline. Horizontal inundation, if
unimpeded by coastal cliffs or other steep typography,
can penetrate hundreds perhaps even thousands of
meters inland.
Vertical run-up of a tsunami is usually 10-50 ft (3-
15 m) high. Wave heights averaged 80 ft (24 m) above
sea level along the western coastline of Sumatra dur-
ing inundation of the 2004 Indian Ocean tsunami
earthquake.14 A 230 ft (70 m) wave was recorded fol-
lowing the 1964 Alaska earthquake.15 Extremely rare
megatsunamis produced by giant submarine land-
slides have been implicated globally.9The highest
megatsunami wave ever witnessed occurred at Lituya
Bay, AK, in 1950. It was triggered by an 8.0-magnitude
earthquake-induced landslide and reached the height
of 1,720 ft (524 m) above the shoreline (three stories
higher than the former World Trade Center of New
York City).3
As the tsunami enters shallow water near coast-
lines, the kinetic energy previously spread throughout
the large volume of ocean deep ocean water becomes
concentrated to a much smaller volume of water,
resulting in a tremendous destructive potential as it
inundates the land. Successive crests may arrive to
shore at period intervals of every 10-45 minutes. This
phenomenon is particularly problematic when respon-
ders attempt to rescue victims from the water after
the first wave, only to become victimized by subse-
quent waves themselves. A single tsunami event may
comprise up to 12 wave crests. Before inundation of
the wave crest, the sea often appears to recede for an
unusually far distance.
During the 1960 Chilean tsunami that struck Hilo,
HI, this phenomenon tended to attract more people to
the shoreline and into the ocean itself where they were
then caught up in the oncoming wave crest. One village
in Papua New Guinea reportedly recognized this as a
sign of pending tsunami and took protective actions for
shoreline evacuation. In Simelue, Indonesia, an old
song about moving to high ground when the earth
shakes is reported to have saved lives and resulted in a
relatively low death rate compared to neighboring
Sumatra (which was farther from the quake epicenter).
Scope and relative importance of tsunamis
Tsunamis have occurred in all the oceans and the
Mediterranean Sea. About 90-95 percent of the world’s
tsunamis have occurred in the Pacific Ocean due to its
relatively large size and its bordering “Ring of Fire”
comprised major tectonic subduction fault zones.
Great trans-Pacific tsunamis are typically caused by
massive earthquakes located at these subduction
zones and occur at an interval of about once a decade.1
Since 1900, there have been 52 tsunami events
worldwide that resulted in at least one fatality.16
During the 1990s, a total of 82 tsunamis were reported
worldwide—a rate much higher than the historical
average of 57 per decade (likely a result of better report-
ing).6During the past decade since 1992, 14 tsunami
events have caused more than 182,059 deaths, and at
least US$ 267 billion in damage16 (see Table 1).
The 2004 Indian Ocean tsunami alone killed
165,708 people (91 percent of all tsunami deaths since
1990) and directly affected two million people in 12
nations.16 WHO has estimated the number of injuries
that required treatment as a result of the 2004 Indian
Ocean tsunami at about 500,000.17
In a 100-year period from 1895 to 1995, there were
454 tsunamis recorded in the Pacific, the deadliest 94
killed more than 51,000 people.3Over the past century
in Japan, ~15 percent of 150 tsunamis were damaging
or fatal. More than half of the 34 tsunamis that struck
Indonesia in the past 100 years were damaging or
fatal. More than 200 tsunamis are known to have
affected the United States since the time of first writ-
ten records. Total damage is estimated at half $1 bil-
lion and 470 casualties, primarily in Alaska and
Hawaii.3Because of its mid-ocean location, Hawaii is
especially vulnerable to such Pacific wide tsunamis.
Twelve damaging tsunamis have struck Hawaii since
1895. In the most destructive, 159 people died there in
1946 from killer waves that were generated almost
www.disastermedicinejournal.com 34 3

2,300 miles (3,700 km) away in Alaska’s Aleutian
Islands.3
The Alaska Aleutian subduction zone poses an
immediate tsunami threat to the western coast of the
United States. Another major tsunami threat is located
off the coast of Washington state or Oregon and northern
California, known as the Cascadia subduction zone.The
probability of a major earthquake occurrence before
2045 is estimated at 35 percent along this zone.
A Cascadia-born tsunami disaster could cost the region
between $1.25 billion and $6.25 billion.6A megatsunami
resulting from the collapse of La Palma, Canary Islands,
could strike the Caribbean, Florida, and the rest of the
US eastern seaboard with a vertical run-up of 164 ft (50
m) high and a horizontal inundation of 12 miles (20 km)
inland.11
The human health effects of tsunamis cannot be
understated. In addition to the public health and med-
ical consequences of these disasters, the socioeconomic,
cultural, and psychological impact of tsunamis has had
an enormous and long-lasting impact throughout the
world and a direct effect on human development in
general. Total damage and losses after the 2004 Indian
Ocean tsunami are estimated at US$ 4.5-7 billion.
$174 million of those losses were incurred by the
healthcare system with an estimated health sector
reconstruction cost in the order of US$ 107 million.17
The World Bank has estimated that damages due to
the 2011 Japan tsunami may range from US$ 122 to
265 billion (2.5-4 percent of Japan’s GDP).2
Factors that contribute to the tsunami problem
Despite the remarkable advances in tsunami moni-
toring and early warning, death tolls remain remark-
ably high. The high death tolls are partly due to
increases in coastal population and high-risk land use
patterns. Settlement patterns increasingly place dense
population near the tsunami hazard. In addition, the
overwhelming majority of coastal communities located
in the tsunami-prone Pacific basin have no direct link-
age to the multimillion dollar Tsunami Warning System.
Most nations at risk lack the resources necessary
to effectively warn and evacuate coastal population.
After the Chilean earthquake of 2010, experts have
debated how much emergency response planners
should rely on tsunami forecasts.18 Difficulties in mod-
eling and predicting the vertical run-up of tsunamis,
as they approach the shore, also contribute to a degree
of uncertainty in advance warning that may affect the
public’s perception of risk.A false alarm that triggered
the evacuation of Honolulu on May 7, 1986 cost
Hawaii more than $30 million in lost salaries and
business revenues.6Even the most reliable warning is
ineffective if the people do not respond appropriately.
Therefore, community education is perhaps the most
important aspect of any tsunami mitigation program.
American Journal of Disaster Medicine
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34 4
Table 1. Fatal tsunami/earthquake disasters
1992-2011
Year Location
Estimated
damage
(US$ million)
Fatalities
1992 Nicaragua 25 179
1992 Indonesia 100 2,500
1993 Japan 1,000 239
1994 Indonesia 2.2 239
1994 Philippines 3.7 81
1995 Mexico 21.1 6
1996 Indonesia 1.2 9
1996 Peru Not available 7
1996 Indonesia 4.2 161
1998 Papua New
Guinea Not available 2,182
2004 Indian
Ocean 4,500 165,708
2009 South Pacific 160 186
2010 Chile 30,000 562
2011 Japan 235,000
21,911
(as of March
21, 2011)
1990-2011 Totals 267,820.4 182,059
Source: Centre for Research on the Epidemiology of
Disasters.16

Factors affecting tsunami occurrence and severity
The effects of the tsunami may vary with factors
including proximity to the earthquake epicenter, physi-
cal geography of the region, the force of the waves when
they hit the shore, and the extent to which the waves
penetrate the shoreline. Proximity to the epicenter of
the earthquake or submarine landslide is directly asso-
ciated with an increased severity due to the amount of
seismic energy transferred during vertical run-up and
horizontal inundation. In the 2004 Indian Ocean
tsunami, Indonesia (the closest land to the epicenter)
suffered the most severe tsunami strikes, followed by
Andaman Nicobar, Thailand, Maldives, Sri Lanka,
India, and eastern Africa as distance from the epicenter
increased.
Refraction by bumps, grooves, and troughs on the
seafloor can shift the wave direction, especially as it
travels into shallow water. In particular, wave fronts
tend to align parallel to the shorelines with a wrap-
around protruding head land before smashing into it
with greatly focused incident energy.6This author
observed this phenomenon as particularly evident in
the total destruction of the cities of Banda Aceh, and
Calang, Indonesia,where the waves entered and exited
the headlands from both sides of the peninsula-like
headland. After the 1946, Aleutian Island earthquake
vertical run-ups in the Marquesas (4,660 miles or
7,500 km from the source) were larger than in Hawaii
(2,300 miles or 3,700 km closer) due to a funneling
effect in narrow valleys.4
The effects of tsunamis on coastal areas are char-
acterized by the maximum destructive force of the
water’s edge. Damage farther inland is potentially
high even though the force of the wave has diminished
because of the floating debris that batters the inland
installations. Low-lying coastal areas and coral atolls
(such as the Maldives) also suffer an increased sever-
ity of destruction.
Public health impact: historical perspective
There is strong evidence that an 8-magnitude
earthquake generated along the Cascadia fault zone
shook the northwest coast of the United States causing
a tidal wave that hit the Japanese island of Honshu on
January 26, 1700.12 It is believed that a tsunami killed
more than 30,000 people within 75 miles (120 km) of
the catastrophic eruption at Krakatau, Indonesia, vol-
cano in 1883. Of the 12 most deadly tsunamis during
1900-2011, four occurred in Japan and four were in
Indonesia, with all but two originating in the Pacific
Ocean. Most resulted in several hundred to several
thousand deaths per event.16
The 1946 Aleutian island tsunami was the most
destructive in the history of the Hawaiian Islands.
More than 150 persons were killed, while damage to
property amounted to $26 million. The United States
reacted to this disaster by setting up the Pacific
Tsunami Warning Center in Hawaii in 1948.6
Earthquake-triggered landslides have the poten-
tial to create tsunamis much larger than expected for
the size of the earthquake. In 1998, the Papua New
Guinea tsunami generated waves up to 50 ft (15 m)
high, killing 2,200 people after a 7.1-magnitude earth-
quake. Two rare landslides in the western Atlantic
also fuel the tsunami concern in the eastern United
States. In 1929, an earthquake-triggered landslide off
Newfoundland’s grand Banks generated a tsunami
that killed 51 people.19
The single largest tsunami disaster in recorded
history occurred in the Indian Ocean on December 26,
2004 along the Andaman Nicobar fault zone. The
tsunami killed more than 165,000 people and dis-
placed 2 million persons in 12 nations. Most recently,a
powerful 9.0-magnitude earthquake hit Japan on
March 11, 2011, unleashing massive tsunami waves
that resulted in widespread damage and destruction.
According to the Government of Japan as of March 21,
at least 21,911 were dead and missing and 2,644
injured.20
Factors influencing mortality and morbidity
Mortality trends
The vast majority of tsunami-related deaths occur
immediately.1In a large tsunami, deaths frequently
exceed the number of injured.1,21 The number of
tsunami-related deaths exceeded the number of
injuries caused by the 2011 Japan tsunami by a ratio
of nearly 7:1.20 The vast majority of those causalities
were sustained as a result of the tsunami rather than
www.disastermedicinejournal.com 34 5

the earthquake. Average death rates are believed to be
50 percent for the population affected by tsunami.1
The 30,000 inhabitants of Calang in Aceh province,
Indonesia, suffered an estimated 70 percent mortality
rate during inundation of the December 26, 2004
tsunami.22 International relief efforts are varied, and
their net impact on the outcome of survivors is beyond
the scope of the present review.
Most tsunami deaths ultimately result from
drowning. However, the tsunami does not consist only
of water. It also contains a great amount of very heavy
debris traveling with tremendous momentum. The
2004 Indian Ocean tsunami and associated debris
were estimated to have been traveling at 30 miles/h
(48 k/h), when on shore in Aceh province, Indonesia.
Deaths from tsunami injuries occur in three
phases. Victims usually succumb to injuries that are
incompatible with life (drowning, severe head, chest,
and spine injuries) within the first few minutes. Then,
immediate complications set in over the next few min-
utes to hours (such as bleeding, lung collapse, and
blood clots in the lung). Finally, these immediate
causes of death are followed by delayed complications
over the coming days that are mostly associated with
infectious disease (such as wound infections and aspi-
ration pneumonia).23,24
According to a recently conducted survey by
Oxfam, four times as many women than men were
killed in the tsunami-affected areas of Indonesia, Sri
Lanka, and India.25 Some of the reasons postulated for
this are similar across these countries: women died
because they stayed behind to look for their children
and other relatives and/or women in these areas often
cannot swim or climb trees, which meant that they
could not escape. There are no published reports of
special risks or means to reduce mortality specific to
children in tsunamis.
Tsunami-associated illness and injury
A tsunami directly injures the victims by the
mechanism of blunt trauma and penetrating injury.26
People are bludgeoned by concrete slabs and felled
trees, stabbed by jagged sheets of metal and glass, tan-
gled up in manacles of wire, and impaled onto tree
limbs and bamboo. Soil, small pieces of wood, glass,
and metal in the contaminated saltwater penetrate
the soft tissues of the body at high velocity. During the
2004 Indian Ocean tsunami, the predominant pattern of
injury comprised multiple large-scale soft tissue wounds
of lower extremities and open fractures.26 Wound con-
tamination was also a major clinical problem.24
When the 2004 Indian Ocean tsunami hit the
western coast of southern Thailand, six to eight huge
waves with a height of 15-22 ft (5-7 m) destroyed
almost everything along the beach and inundated
areas more than 984 ft (300 m) from the seashore.
Most of the survivors had minimal to moderate
injuries to the body and extremities.27
No survivor of the Papua New Guinea tsunami
was found to have head, spine, thorax, or abdomen
injuries, implying that survival of these life-threaten-
ing injuries was virtually impossible in that remote
setting with delayed resuscitative and surgical care.26
Bone fractures, soft tissue injuries, and near-drowning
were the most common conditions reported among
survivors in both the Papua New Guinea and the
Indian Ocean tsunamis.27-29
Infectious diseases
The role of active case finding and generous avail-
ability of health services surely played a role in the noted
eightfold increase of acute respiratory infections in Aceh
province, but it can generally be agreed that acute respi-
ratory infection did increase substantially following the
2004 tsunami. Cases of acute respiratory infections
decreased significantly after the first 5 weeks suggesting
that the largest caseload occurs within a month after the
disaster event and is related to tsunami-induced near-
drowning as a major causative factor.30
Near-drowning is common in tsunamis and is fre-
quently associated with aspiration pneumonia or
“tsunami lung,” a necrotizing pneumonia notable for
flora commonly associated with sea water near-drown-
ing (eg, Aeromonas and Pseudomonas species).
However, cultures from the upper respiratory tract
specimens also grew an unusually high rate of rela-
tively uncommon pathogens that are not associated
with sea water aspiration (such as multiple-resistant
Acinetobacter baumanii, methicillin-resistant Staphy-
lococcus aureus,Stenotrophomonas maltophilia,
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Burkholderia pseudomallei, and Candida albi-
cans).24,28,31
Melioidosis, a serious infection caused by B.
pseudomallei is reported most commonly in Southeast
Asia and northern Australia. The infection is acquired
by contamination of breaks in the skin or by inhala-
tion. Several cohorts of patients in southeast Thailand
and the Phuket area were diagnosed with melioidosis
after aspiration related to the Indian Ocean tsunami.
Immunocompromise was an associated risk factor as
would be expected.23,32,33
Tsunami wounds are inevitably contaminated
with soil, debris, and foreign bodies. Wound infections
were common after the 2004 Indian Ocean tsunami
and comprised 16.9 percent of all diagnoses by
January 10 at the International Committee of the Red
Cross (ICRC) field hospital in Calang, Indonesia)22
and 15 percent of all consultations at the ICRC field
hospital in Banda Aceh.30
Similar to acute respiratory infections, wound infec-
tions also frequently involved multiple, relatively
uncommon pathogens, such as Pseudomonas aerugi-
nosa,S. maltophilia, and Klebsiella pneumoniae.24,29,34
Acute open marine trauma is not infrequently associ-
ated with subsequent infection.24 However, cultures also
indicated significant coexistent contamination with
highly resistant species uncommon to aquatic sur-
roundings such as multiple-resistant A. baumanii,
extended-spectrum beta lactamase producing Escheri-
chia coli, methicillin-resistant S. aureus, and Candida
species. One case report described multifocal cutaneous
mucormycosis complicating polymicrobial wound infec-
tions in a tsunami survivor from Sri Lanka.34
As was also the case in population affected by hur-
ricanes Andrew and Iniki, tetanus cases increased
after the 2004 Indian Ocean tsunami as a result of
soil-contaminated injuries sustained at the time of
impact. The number of cases then returned to baseline
within 1 month of the event signifying that all cases
were the result of wound contamination sustained
during the tsunami event itself.30
The correct identification of pathogens and their
antimicrobial susceptibility is essential to reduce mor-
tality, especially in the cases of wound infections and
unusual respiratory infections after tsunami. Therefore,
sufficient diagnostic and confirmation capacities such as
radiology and laboratory services should be made avail-
able. For this reason, emergency medical teams should
be aware of resistance patterns in the target areas
before or shortly after arrival to appropriately respond
to the situation. Emergency health kits should include
medications that offer appropriate broad-spectrum
antimicrobial coverage for such infections as those that
would be expected after tsunami.
Contrary to initial concerns for outbreaks of
malaria, measles, cholera, and dengue,35-39 the Indian
Ocean tsunami (like the overwhelming majority of all
previous seismic disasters) was not associated with
epidemics of infectious disease.30 There are no data to
explain why tsunamis do not appear to be associated
with epidemics of infectious diseases.
Despite reports of a significant risk of vector abun-
dance with enhanced transmission potential,40 no
increases in cases for malaria or dengue were noted in
any nation of the tsunami-affected regions of Southeast
Asia.30 Ironically, the post-tsunami monthly incidence
of malaria in Aceh province, Indonesia, was more than
10 times lower than the comparable monthly rate over
the last 5 years before the 2004 tsunami.30 Experience
has shown that these diseases, however commonly
believed, are not always a priority immediately after
any natural disaster.30
Psychosocial consequences
Behavioral health effects are among the most
chronic and debilitating outcomes of natural disasters,
including tsunamis.41,42 Clinical symptoms of post-
traumatic psychological stress response have been
widely noted among tsunami survivors and relatives.24
Among survivors of the tsunami in southern
Thailand, elevated rates of symptoms of post-trau-
matic stress disorder (PTSD), anxiety, and depression
among adults were reported 8 weeks after the disaster
with higher rates for anxiety and depression than
PTSD symptoms. Nine months after the disaster, the
rates of those reporting the symptoms decreased but
were still elevated.43
Prevalence of PTSD symptoms among children in
displacement camps of southern Thailand was ele-
vated when compared with nonaffected villages. After
www.disastermedicinejournal.com 34 7

9 months, the prevalence of PTSD symptoms among
children’s and camps had not significantly decreased.44
The monumental devastation of the December
2004 Indian Ocean tsunami also prompted a meta-
analysis of the psychosocial consequences of natural
disasters in developing countries versus developed
countries. A much higher proportion of the population
in developing nations sustained severe loss and
extreme trauma and experiences that constitute clini-
cally significant distress when compared with devel-
oped nations (for not only tsunamis but also all
natural disasters in general).42,45
Summary
Tsunamis represent a significant public health
hazard for coastal population located near tectonic
subduction zones. The public health impacts of
tsunamis are well known and predictable. The over-
whelmingly most significant health impact is that of
mass fatalities due to drowning. Secondarily, other
health impacts are related to traumatic injuries, dis-
ruption of the public health infrastructure, population
displacement, and psychological stress.
Acknowledgments
The material in this article solely reflects the views of the
author. It does not necessarily reflect the policies or recommenda-
tions of the Centers for Disease Control and Prevention or the US
Department of Health and Human Services.
Mark E. Keim, MD, Senior Science Advisor, Office of Terrorism
Preparedness and Emergency Response, National Center of Envi-
ronmental Health, Agency for Toxic Substances and Disease
Registry, Centers for Disease Control & Prevention, Atlanta,
Georgia; Adjunct Professor, Rollins School of Public Health,
Emory University, Atlanta, Georgia.
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