An eco-epidemiological analysis of Dengue outbreak in Port Blair, South Andaman Island, India, during 2022

In Port Blair, the capital of Andaman & Nicobar Islands, in the Bay of Bengal, there was a sudden increase in fever cases resembling the symptoms of dengue in the monsoon period of 2022. Hence, an investigation was carried out to find out both epidemiological and entomological reasons behind the outbreak.

An Entomological survey was carried out in 24 wards of Port Blair Municipal Council (PBMC) area, epidemiological data of last six years (January to December of 2017-2021 & January to October of 2022) and patient details of the year 2022 were collected. Both the epidemiological and entomological data were analyzed concerning time and place.

During this outbreak period tyres (22.4%) came out as a major breeding habitat followed by small discarded materials (17.5%), metal drums (15.3%), and plastic drums (11.7%). In rainy season peri-domestic breeding (55%) was more than the domestic breeding (45%) habitat. Ae. aegypti had a high preference for indoor large containers (100-1000 L) like plastic tank, metal drum and cement tank whereas Ae. albopictus prefers to breed in medium sized plastic container (20-100 L) and outdoor water receptacles like tyres, flower pots, domestic discarded materials etc.

By source reduction, indoor space spray and outdoor fogging vector density was controlled which curtailed the transmission and within 8 weeks decreasing trend of dengue cases were noticed. A regular entomological survey is very important to know the seasonality and key breeding habitats of the vector for proper planning of vector control.