Spatio-temporal distribution of dengue cases and vectors along with the interrelationship of environmental and climatic factors in the metropolitan city, Kolkata, India, for 2017-2022: calling implications for vector control.

We studied the spatio-temporal distribution of dengue at the micro-scale, along with other important factors for disease transmission, like vector prevalence, seasonality, breeding behaviour, entomological indices, and its relation with environmental and climatic factors in Kolkata, one of the most populous metropolitan cities in India, facing dengue upsurge in recent years. We analysed dengue data from 144 wards, city-level meteorological data for 6 years (2017-2022), Land Use Land Cover (LULC) data for 2022, and entomological surveillance data from 7 wards in 2022. Dengue showed high spatial heterogeneity and clustering at the micro-level, with a yearly post-monsoon peak (August-November) accounting for ∼90% of cases and representing a 2-3 month lag between high rainfall, temperature, and relative humidity (RH). Both Ae. aegypti and Ae. albopictus were prevalent, with distinct spatio-temporal distributions and instances of mixed breeding. Ae. aegypti primarily breeds indoors and peri-domestically, showing a strong correlation with rainfall (R² = 0.78, p-value = 0.0003) in indoor habitats and had a perennial presence. In contrast, Ae. albopictus was the more common outdoor breeder, strongly correlating with rainfall (R² = 0.75, p-value = 0.0003) in outdoor habitats. This is the first study from Kolkata, India, highlighting the spatio-temporal distribution of dengue and its links to vector behaviour, climate, and environmental factors. The findings will help identify recent dengue hotspots in Kolkata, which will help in developing targeted vector control strategies.