International Journal of Preventive Medicine (Int J Prev Med)2008-78021120120218192192ENDepartment of Pathology, Hindu Rao Hospital, Delhi, IndiaDepartment of Pathology, Hindu Rao Hospital, Delhi, IndiaDepartment of Pathology, Hindu Rao Hospital, Delhi, IndiaDepartment of Pathology, Hindu Rao Hospital, Delhi, IndiaDepartment of Pathology, Hindu Rao Hospital, Delhi, IndiaDepartment of Pathology, Hindu Rao Hospital, Delhi, India201105162012021220111114<p><strong>Background: </strong>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&ndash; 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.</p> <p><strong>Methods: </strong>Blood samples were collected from patients with DF-like 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.</p> <p><strong>Results: </strong>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&ndash;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.</p> <p><strong>Interpretation and Conclusion: </strong>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.</p> <strong>Key words: </strong>Delhi, dengue infection, herd immunityhttp://ijpm.mui.ac.ir/index.php/ijpm/article/view/192http://ijpm.mui.ac.ir/index.php/ijpm/article/download/192/626