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Brief Reports Indian Pediatrics 2002; 39:369-372 |
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Epidemiological Factors of Dengue Hemorrhagic Fever in Bangladesh |
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In recent years dengue has become a major international public health concern. Annually there are 50-100 million cases of dengue fever (DF) and 0.25 - 0.50 million cases of dengue hemorrhagic fever (DHF) in the world(1). DHF was reported for the first time in Philliphines in 1957(2). Subsequently, it was also reported from neighboring countries like India, Nepal and Myanmar(3,4). An enormous outbreak of dengue took place in Bangladesh in 2000 and the situation was quite alarming(5). Bangladesh had made an emergency appeal to the WHO to help control the outbreak. Dengue fever although unfamiliar is not unknown in this country. In 1964 this flue like illness was labelled as Dhaka fever(6). Researchers and program managers studying dengue have demonstrated that different geographic areas and socio-cultural practices show a variable response to the infection and accordingly present different epidemiological pattern(7). Moreover, circum-stantial evidence suggests that some popula-tion groups may be more susceptible to vascular leak syndrome than others(8). This study was therefore, designed to evaluate the epidemiological factors of DHF in admitted children in a medical college hospital, which might help in future planning to control the disease. Subjects and Methods In Khulna Medical College Hospital (KMCH), a separate ward was arranged to deal with dengue patients in July 2000. Dengue patients under fifteen were taken care by the Department of Child Health and above that age were cared by the Department of Medicine. Dengue hemorrhagic fever and dengue fever requiring observation were admitted in dengue ward. Only the DHF cases were enrolled in this study. The criteria for diagnosis was based on WHO case definition(9). The evidence of DHF includes a febrile illness followed by one or more of the following: (i) Positive tourniquet test, (ii) Minor or major bleeding mani-festation, (iii) Thrombocytopenia (Platelet count <100,000/cumm; (iv) Hemo-concentra-tion (raised hematocrit >20%). Isolation of virus or serology were beyond the limitation of present study. At the end of December, number of patients came down to zero and the dengue ward was temporarily closed awaiting further breakthrough. A proforma was prepared to take a detailed history of each patient with special emphasis on host factors, e.g., age, sex, residence, education and economy. The habitat beyond metropolitan city and municipality area was considered as rural area. Regarding economy, a monthly income of three to ten thousand taka (60-200 US dollar) was considered as average income group. Results During the period of six months, total patients in dengue ward was 412 and children below 15 years was 125. DHF cases were 115 in number. Total deaths during this period was 18 out of which 8 belonged to children group. The affected children were mostly beyond four years of age and the sex ratio was nearly equal (Table I). The number of admitted patients started with 6 in July, reached its peak (n = 35) in October and gradually declined to 4 in December. Socio economic characteristics are high-lighted in Table II. The proportion of children from urban area was 57.4%. Regarding school status of affected children, it was found that primary school children were the commonest victims. Majority of patients (59.2%) belonged to average income family. All of the fatal cases (n = 8) were above 5 years of age and male female ratio was equal (4 : 4).
Discussion Dengue fever is caused by dengue virus having four serotypes - DEN 1,2,3,4. The viruses are maintained in tropical and sub-tropical areas by the mosquito - Aedes aegypti, a species closely associated with human habitation(1). The environment of Bangladesh is quite favorable for dengue disease. The first formal scientific survey in Bangladesh took place in 1997 in Chittagong Medical College Hospital (CMCH)(10). Out of 255 patients, mean age was 7.2 years and male-female ratio was 1.5:1. The age group of 5-9 years was mostly (57.1%) affected. Report from neighboring countries highlighted that 90% of hospitalized dengue patients are less than 15 years old(9). But we found only 30.3% of patients are children of same age. However, proportionate number of children were more in the later part of the study. Disease trend in most countries revealed that initially it affects people of all ages but gradually, children become the most susceptible group. Immuno-logists also suggest that DHF is more common in children who suffer for the second time. In Thailand case fatality rate of Dengue in 1950 was 13.8% and after standardized clinical management it came down to 0.34% in 1998(12). We encountered the case fatality rate of 7% as a new experience. Majority of affected children in this study belonged to the age group of 10-14 years and the mean age was 9.2 year which was slightly different from another study(10). Female aedes mosquito, the vector of the virus is peridomestic in nature. The tropical zones of the world having monsoon rains is the usual habitat of this vector(9). The breeding of Aedes aegepti is highest during pre and postmonsoon period(10). We found the epidemic in postmonsoon period. A major contributory factors to this increased activity may be due to changes in weather pattern such as El-Nino phenomenon(2). Urban human population constitutes the natural reservoir of Dengue and travellers are the disseminating factor of virus from one country to another(9). Furthermore, the vector resides more in and around town dwellers. We found 57.4% children coming from urban areas. Although the disease started in urban area, later it spread to rural areas as well. The biting of mosquito seems to occur throughout the day but is marked by two distinct peak periods - morning and mid-afternoon(9). So late risers, school students and late evening sleepers are more susceptible to mosquito bite. We agree with the fact that students (80.9%) are the most vulnerable group and primary school children (40.9%) were the majority. However, CMCH survey highlighted that 48.6% patient belonged to mixed primary secondary school(10). In comparison to other communicable diseases, the case fatality of Dengue is not significant, but it raises much hue and cry because it involves mostly the affluent sections of the society(12). Thirty per cent of affected children in this series came from poor income family and only 10.4% from affluent group. This low figure may be due to admission of latter children in private clinics. Contributors: CHR was responsible for the design, draft and interpretation of the study. He will act as guarantor of the paper. HAMNA and AKMMR took part in analysis and revision. MRHK helped in data collection and processing. Funding: None. Competing interests: None stated.
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