[Emerging Infectious Diseases]
[Volume 4 No. 2 / April - June 1998]

Update

International Editors Update

--------------------------------------------------

In this new section, we welcome commentary and updates from our newly
formed Board of International Editors.

Emerging Infectious DiseasesSoutheast Asia

Sai Kit Lam
University of Malaya, Kuala Lumpur, Malaysia

Dr. Lam is professor and head, Department of Medical Microbiology, Faculty of 
Medicine, University of Malaya. He serves on the editorial board of several 
medical journals and is the director of the WHO National Influenza Center, 
the WHO National Center for Rapid Viral Diagnosis, and the WHO Collaborating 
Center for Arbovirus Reference and Research for Dengue and Dengue Hemorrhagic Fever.

The recent emergence of a new strain (H5N1) of influenza A virus, the
so-called avian or bird flu, in Hong Kong underlines the importance of the
Southeast Asia region as an epicenter not only for influenza A viruses but
also for other microbial agents. In late 1992, Vibrio cholerae O139
appeared on the Indian subcontinent; and within a few months, it had spread
to China, Nepal, Pakistan, Malaysia, and as far as Russia.

The World Health Organization (WHO) has reported that infectious diseases
account for more than 17 million deaths per year worldwide and that at
least 30 new infectious diseases have emerged within the last 2 decades. Up
to half of the 5.8 billion people on earth are at risk for many endemic
diseases, with the most overpopulated and economically depressed countries
in Southeast Asia at highest risk. Although vaccines and antibiotics are
available for many diseases, in 1995 alone, respiratory infections such as
pneumonia killed 4.4 million people, 4 million of them children. Diarrheal
diseases, including cholera, typhoid, and dysentery killed 3.1 million,
most of them children. Tuberculosis (TB) killed almost 3.1 million, malaria
2.1 million, hepatitis B more than 1.1 million, and measles more than 1
million.

Faced with the reality of infectious diseases on a daily basis, Southeast
Asian nations have not been able to give emerging disease surveillance the
priority status it deserves. Much of the surveillance in the region is
centered in a few well-established laboratories where there is adequate
expertise, sufficient funding, and personal interest. Because of influenza
A, it is widely believed that Asia is the epicenter of new influenza
strains; the emergence of the avian influenza strain in Hong Kong supports
this contention. As a result of the activities of the Pacific Basin
Respiratory Virus Research Group, an excellent surveillance program for
respiratory viral infections is in place. If this small cluster of avian
flu had occurred elsewhere, it would most likely have been missed. All the
110 WHO Influenza Centers, particularly those in Southeast Asia, have been
alerted and are frequently updated about the Hong Kong outbreak. Diagnostic
reagents for the identification of the H5N1 strain will be made available
to these centers as part of the surveillance program.

Enteroviruses

Enteroviruses are frequently associated with the hot and humid climate of
tropical countries in Southeast Asia. The viruses are responsible mainly
for inapparent and mild infection, but occasionally they can give rise to
infection of the central nervous system, resulting in aseptic meningitis
and (rarely) paralysis; polioviruses are a good example. Hand, foot, and
mouth disease, caused by enteroviruses, such as coxsackie A16 and
enterovirus 71, is common in many countries in the region. In a recent
outbreak of hand, foot, and mouth disease in Malaysia, a new clinical
entity of encephalomyelitis emerged, which resulted in several deaths among
children under 5 years of age. Four such deaths were investigated
thoroughly in the University Hospital in Kuala Lumpur. All four children
were seen in the Emergency Department in a state of respiratory and
cardiovascular instability with a history of fever (3 to 5 days) associated
with reduced oral intake. One child had flaccid paralysis with hyporeflexia
of the lower limbs. A constant feature in these patients was the very rapid
vascular changes, followed rapidly by cardiac decompensation. Pulmonary
edema followed, suggesting a concomitant increase in pulmonary vascular
permeability. Consent for postmortem was obtained with some difficulty
because of religious and cultural reasons. The midbrain, pons, medulla, and
spinal cord were extensively damaged, with the worst damage at the level of
the medulla. The cerebrum and myocardium were relatively normal.
Enterovirus 71 was isolated from the medulla and spinal cord of three
children and from the cerebrum of the other child, where no brain stem
material was available. Other tissue sites including the cerebrospinal
fluid did not yield virus. The need for postmortem examinations in
investigating fatal emerging diseases must be addressed in areas where such
examinations are not possible for cultural reasons.

Arboviruses

Arthropod-borne viruses or arboviruses are yet another group of viruses
synonymous with countries in the region and cause considerable sickness and
death. Some of these viruses, e.g., Murray Valley encephalitis virus in
Australia, have restricted geographic distribution but may have the ability
to transcend geographical barriers, as in the emergence of Japanese
encephalitis virus in the Torres Strait of northern Australia and in Papua
New Guinea.

Dengue

Dengue is by far the most important arbovirus infection in Southeast Asia.
According to WHO, dengue has been reported in over 100 countries worldwide
and poses a threat to approximately 2 billion people. At the 46th World
Health Assembly held in Geneva in May 1993, a resolution was passed to make
the prevention and control of dengue a priority.

Dengue is an acute viral infection characterized by abrupt onset of fever,
severe headache, pain behind the eyes, muscle and joint pains, and rash.
The hemorrhagic form of dengue fever, dengue hemorrhagic fever (DHF), was
recognized as a new disease in the Philippines in 1953 and has been seen in
India, Malaysia, Singapore, Indonesia, Vietnam, Cambodia, and Sri Lanka.
During 1956 to 1992, 1,335,049 cases of DHF (13,723 deaths) were recorded
in Vietnam alone. The rise of dengue in tropical and subtropical areas of
the world is explained by factors such as rapid population growth,
expanding urbanization, inadequate municipal water supplies, and
difficulties in refuse disposal. These lead to an abundance of new breeding
sites for the mosquito vectors, while human migration patterns disperse
vectors and viruses into new areas.

The resurgence of DHF in several countries where only dengue fever had been
reported has become worrisome. Sri Lanka reported its first outbreak in
1989, and India and China also faced the same dilemma. DHF/dengue shock
syndrome has also been reported for the first time in New Caledonia and
Tahiti. The large outbreak in Cuba in 1981 showed how the disease has
spread to the Americas and other countries such as Venezuela and Brazil. In
Malaysia, where the disease is endemic, encephalitis cases associated with
dengue viruses have been documented, and vertical transmission has also
been reported in the last two years. Other unusual manifestations observed
rarely include acute renal failure and hemolytic uremic syndrome. The
emergence of such unusual clinical manifestations should also be monitored
and documented in other dengue-endemic countries. Despite intensive efforts
by the countries in the region to control the vectors, the disease is still
on the rise. A tetravalent live attenuated vaccine developed at Mahidol
University, Thailand, is being field-tested, and the preliminary results
are promising.

Disease Spread

Rapid transportation has been blamed for the spread of diseases, and this
is especially so in countries in the region. Tourism is an important
industry in Southeast Asia, and a series of conferences on travel medicine
has highlighted the problems, particularly in infectious diseases. Another
vast movement of people between countries in the region is that of migrant
workers. In Malaysia, an estimated 1.7 million workers are migrant workers,
of which only 1.2 million came in legally. Most of the workers are from
Indonesia, Myanmar, Philippines, and Pakistan, and they work in the
agricultural sector as well as in construction and domestic services. Those
who come in legally undergo a medical examination that includes screening
for some infectious diseases. Diseases associated with migrant workers are
chloramphenicol-resistant typhoid, multidrug-resistant TB, leprosy,
malaria, HIV/AIDS, and filariasis. In 1993, the first case of kala-azar
caused by Leishmania donovani was reported in a Bangladeshi migrant worker
in Malaysia, and since then, four other cases have been identified, all of
them in Bangladeshi workers. This disease had not been present in Malaysia.

In 1997, the theme "Emerging Infectious Diseases: Global AlertGlobal
Response" was chosen by WHO to celebrate World Health Day. This year, as
WHO celebrates its 50th anniversary, the region is still plagued with major
public health problems threatening the lives of millions of people in the
region. These problems underline the need to strengthen epidemiologic
surveillance and concentrate public health activities in Southeast Asia,
the epicenter of many emerging diseases.

Address for correspondence: S. K. Lam, Department of Medical Microbiology,
Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia; fax:
603-758-2801; e-mail: lamsk@medicine.med.um.edu.my.

Emerging Infectious Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention
Atlanta, GA

URL: http://www.cdc.gov/ncidod/EID/vol4no2/update.htm

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