Warming climate may sharpen Kerala's dengue risk, IITM study finds
An IITM-led study links Kerala's dengue burden to temperature, humidity, rainfall and El Niño, and offers a machine-learning model that predicts cases months in advance.
Kerala's already warm and humid climate creates conditions that favour dengue transmission for much of the year, and El Niño can intensify that risk, according to a study led by researchers at the Pune-based Indian Institute of Tropical Meteorology (IITM).
The work, led by climate researcher Sophia Yacob and published in GeoHealth, identifies temperature, humidity, El Niño–Southern Oscillation (ENSO) conditions, rainfall, and the active and break phases of the monsoon as the main climate indicators associated with dengue cases in the state.
El Niño years are marked by unusually warm sea-surface temperatures in the central and eastern equatorial Pacific. Co-author Roxy Mathew Koll said the study found a combination of weather factors, across both the pre-monsoon and monsoon seasons, shaping dengue incidence in Kerala, with variations even within the state.
"Kerala experienced humid and warm temperatures for long periods in the year. This means availability of favourable climatic conditions for higher transmission of dengue," Koll said. El Niño-like conditions, he added, shift large-scale circulation towards warmer and drier pre-monsoon conditions over the state, increasing dengue incidence.
Kerala's pre-monsoon window from March to May is characterised by high temperatures, high humidity and thunderstorms. Dengue cases typically begin rising in May and peak in June and July, with close to 60 per cent of the state's annual cases reported during the Southwest Monsoon from June to September.
To translate these links into usable forecasts, the team built a machine-learning model that combines real-time climate forecasts with health surveillance data. The model can predict up to 72 per cent of the variation in dengue cases, the researchers reported, and they suggest it could be extended to similar vector-borne diseases as well as viral or seasonal influenza.
Because climatic signals arrive at different points in the year, the researchers say Kerala can prepare for vector-borne disease outbreaks up to five months in advance. El Niño years present an added challenge, as warmer pre-monsoon conditions raise the likelihood of greater dengue risk during the monsoon.
The IITM team had earlier examined dengue patterns in Pune and plans to extend its work on climate and vector-borne disease to Chennai and Bhopal.