http://www.dailytimes.com.pk/default.asp?page=2011\11\05\story_5-11-2011_pg3_3
Saturday, November 05, 2011
VIEW: Dengue fever: research and prevention —Dr Arif Nawaz
A vaccine for the dengue virus is in the final phases of testing.
However, the usage of this vaccine (when available) will have to be guided by
sound epidemiologic data in order to ensure maximum efficacy
Dengue fever has become the second most prevalent mosquito-borne
infection after malaria in recent decades. The epidemic has reached almost 120
countries with the most endemic regions being Southeast Asia, Latin America,
Asia, and the Caribbean. Although dengue has been a problem in the Indian
subcontinent for almost a century, the last two decades have seen a resurgence
of this disease in Sri Lanka, India, the Maldives Islands, Bangladesh, and
Pakistan. There is a lack of valid data on reported cases of dengue fever and
its life-threatening complication, dengue hemorrhagic fever (DHF) for Pakistan
until 1994 when a major outbreak occurred. The last few years have seen a major
surge in the number of cases of dengue fever, particularly in urban Punjab.
This year extraordinary measures on the part of the provincial government were
needed to control this epidemic. However, this disease managed to take a
significant toll in terms of lost human lives, morbidity and financial strain
on a public reeling under the pressures of an economic downturn. We need a
better understanding of the epidemiology of dengue in this region to develop
and implement effective control programmes and to most effectively use dengue
vaccines that are currently in clinical trials.
Climate and environmental aspects play a critical role in the
distribution and prevalence of both the dengue virus and its vectors (Aedes
aegypti and Aedes albopictus). During the monsoon season (June to September),
ideal conditions for the vectors exist and most dengue cases are recorded
between September and November, with the highest numbers seen in
September-October. The dengue fever complex consists of four distinct serotypes
(1-4). Infection with one serotype provides lifelong immunity against the same
type but not against others. Thus, people can be infected with multiple
serotypes during their lifetime. People with a repeat infection have a greater
risk of developing life-threatening complications due to cross-reactive
immunity. It is, therefore, imperative that effective disease surveillance be
in place to monitor and predict changes in the behaviour of the disease.
Effective measures can then be implemented to control it. If no control
measures are taken or if they are not guided by these scientific principles,
each successive year will witness an increasing morbidity and mortality from
this disease.
The provincial government of Punjab lauded the role of the Sri Lankan
team that helped the local health experts in controlling this disease. It is,
therefore, pertinent to see how the Sri Lankans with limited resources managed
to control this epidemic. Dengue outbreaks in Sri Lanka date back to the early
1900s with many major outbreaks occurring between 2003 and 2006. Dengue fever
and DHF are reportable diseases in Sri Lanka. All practicing doctors treating
dengue patients are expected to report cases to local health officers, who
report cases on a weekly basis to the Central Epidemiology Unit of the Ministry
of Health in Colombo. Researchers feel that this mechanism has resulted in very
accurate reporting of dengue fever cases. Such reporting is supplemented by
periodic surveillance studies of the general population to define prior
exposures to this disease. Genentech Molecular Diagnostics Institute in
Colombo, Sri Lanka, receives diagnostic specimens for dengue testing from
clinics and hospitals in Colombo. This data is used by the local health
authorities in consultation with global health experts who are then able to
identify the changing trends of the virus at a cellular level as well as
epidemiologically. This information is then used effectively to implement
public health measures that contain the virus and its vector as well as
identify high risk groups. With this information, healthcare authorities in the
future will be able to identify populations that are likely to benefit from
vaccination (when available).
Healthcare experts had predicted a major epidemic this year. However, the
preventive measures need to be strengthened to eradicate this disease. The will
on the part of the government to eradicate this menace has to be supported by a
scientific approach to the problem. Control of this disease included recent and
past surveillance data and virus isolates to better understand factors driving
the emergence of severe disease. This information can be used to design
interventions to control the vector and virus of this disease. Public health
measures including training of health personnel, increasing the awareness level
of the general public about this disease and vaccination (when available) are a
must if we want to eradicate this threat. These measures are most effective
when the trends and patterns of this disease have been defined as mentioned
above. A vaccine for the dengue virus is in the final phases of testing.
However, the usage of this vaccine (when available) will have to be guided by
sound epidemiologic data in order to ensure maximum efficacy. Urgent research
in this field is needed to direct future interventions. Failure to follow the
scientific approach in controlling dengue fever can not only have devastating
effects on our population but will also result in wastage of scarce healthcare
resources.
The support of NGOs and the private sector, as mobilised in the recent
episode by the government, is mandatory. The slogan of my institution, Fatima
Memorial System is: “Alone we can do little; together we can change the world.”
The writer is Vice-Principal Clinical Affairs, NUR/FMS, Professor of
Medicine and Head, Division of Gastroenterology and Hepatology at NUR/FMS
[Non-text portions of this message have been removed]
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