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
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