Endemic Dengue Fever: A seldom recognized hazard for Pakistani children

Background: Dengue fever (DF) has gained prominence as an epidemic disease in Pakistan in the recent years. However, little data exists to show its likely endemic nature. Methodology: We retrospectively analyzed blood for dengue IgM on samples obtained during a community-based surveillance for febrile illnesses in two slum areas of Karachi, Pakistan, between June 1999 and December 2001. In this period, no epidemic of DF occurred in the city. Participants were children older than 16 years who had fever ≥ 38°C for more than 72 hours and in whom other common infections were excluded, based on clinical examination and laboratory tests (blood culture, urinalysis, complete blood count, Typhidot® test and peripheral blood film for malaria). Results: One hundred and fourteen blood samples were analyzed for dengue IgM ELISA, out of which 54 (47.4%) tested positive. The incidence of DF in this community was possibly as high as 185 (95% CI: 145 - 242) per hundred thousand population/year. Older children (10-15 years) appeared 5.5 times more likely to be affected than their younger (0-5 years) counterparts. Conclusions: DF is probably endemic in children in slums of Karachi, and likely to have high incidence rate. Older children are more susceptible to the disease. Further prospectively designed research is needed to confirm these findings. Until that time, DF may be included in the differential diagnosis of fever without focus in children in Karachi slums even in non-epidemic periods.