Dengue fever outbreak by more than one serotype in a municipal area of Kolkata, Eastern India.

A dengue outbreak struck Baranagar municipality area of North 24 Parganas district, West Bengal in July 2016. This study presents the epidemiological and virology findings of this outbreak. The outbreak started from 17 July and continued until 17th December. Total 1660 dengue cases (overall attack rate: 7/1000) and two deaths (case fatality rate: 1/1000) were reported. All age groups were affected. Out of the 213 blood samples collected from probable dengue cases and tested at Virus Unit, ICMR-National Institute of Cholera & Enteric Diseases (NICED), Kolkata, 163 (76%) tested seropositive through NS1 / IgM ELISA confirming dengue infection. DENV 1 was the predominant (53%, 44/83) serotype followed by DENV 2 (23%, 19/83), DENV 4 (15.6%, 13/83), DENV 3 (8.4%,7/ 83). Coexistence of dengue and chikungunya virus infection was detected. Major presentation of the confirmed dengue cases was fever with headache (95%), followed by arthralgia, myalgia, retro-orbital pain, abdominal pain, diarrhoea, and rash. Abundance of vector breeding spaces was observed in the area. Accordingly the health authorities were suggested to conduct frequent mass awareness campaigns involving community to reduce breeding sources during pre-monsoon and monsoon months. Further, adult mosquito control measures were also suggested throughout the year and inter-departmental coordination was recommended for prevention of such outbreaks in future.