Dengue fever in a rural area of West Bengal, India, 2012: an outbreak investigation.

Background: During September 2012, an increased number of fever cases was reported from Ramnagar-II block, Purba Medinipur district. This study investigated the outbreak, with the following objectives: to describe the distribution of fever cases, to determine the risk factors and to recommend preventive measures.

Materials And Methods: The clinical features, date of onset and outcome of all cases of fever were listed. Blood specimens were collected from affected patients and sent for serological examination. An epidemic curve was plotted and environmental and entomological surveys were carried out.

Results: There was a total of 100 cases, of which 56% (56/100) were men.Among the four villages studied, the highest number of cases was from Gopalpur 37% (37/100), followed by Badalpur 26% (26/100); 19% (19/100) of cases had a history of migration from dengue-endemic areas. The majority of cases were in age group 15-45 years - 52% (52/100), followed by the age group >45 years - 28% (28/100). All the cases had history of fever (100%), followed by myalgia - 82%, headache - 78%, and retro-orbital pain - 73%. The outbreak started on 7 September 2012, peaked on 18 September, then gradually declined and no further cases were noted after 28 September 2012. Seventy-nine percent (79/100) of cases were NS1 test positive (non-structural antigen-1) and 72% (13/18) cases were positive on a dengue monoclonal antibody (IgM) capture enzyme-linked immunosorbent assay (MAC-ELISA) test. All recovered except one (case-fatality ratio: 1%). The values for Household Index, Container lndex and Breteau Index of the four villages were: Badalpur, 3%, 10% and 5%; Gopalpur, 13%, 23% and 18%; Ramchandrapur, 9%, 11%, and 13%; and Tajpur, 2%, 2% and 2%.

Conclusion: The outbreak was probably due to dengue fever. The study led to a recommendation to destroy water containers and use mosquito nets. The outbreak was controlled.