Seroprevalence and Trend of Dengue Cases Admitted to a Government Hospital, Delhi – 5-Year Study (2006-2010): A Look into the Age Shift

Background: Diagnosis of dengue infection is easily and best accomplished by demonstration of specific IgM antibodies in blood. We analyzed retrospectively the dengue IgM seropositivity available for samples obtained over a period of 5 years (2006– 2010) from patients with suspected dengue fever (DF)-like illness to investigate whether there was an overall increase in the dengue IgM prevalence over this period. Methods: Blood samples were collected from patients with DFlike febrile illnesses attending the Pediatric, Medicine, and Fever clinics of a Government hospital, Delhi. A total of 8138 individuals (suspected dengue cases) obtained over 5 years were tested for dengue specific IgM antibodies. Year wise, month wise, and age wise data on geographic distribution and clinical manifestations were analyzed. Results: Of the 8138 samples, 1600 (19.66%) were positive for dengue specific IgM. The year 2006 had the highest number of reported cases, 761 (46.23%). In our study, the age group most commonly affected of all 5 years was 11–20 years. Out of the total 1600 cases admitted to the hospital between 2006 and 2010, 279 (58.9%) had DF, 178 (37.6%) had dengue hemorrhagic fever, and 16 (3.38%) had dengue shock syndrome. We found a high burden of dengue in young children and late adolescents in both rural and urban communities at a magnitude greater than previously described. Interpretation and Conclusion: We observed an increase in the dengue positive cases every alternate year, thereby indicating a possible role of herd immunity in northern India. We did not find a steady increase in the number of cases over 5 years. We found an increase in the number of positive cases in children and young adolescents.