How climate change could reshape Kerala’s dengue threat

El Niño-driven changes in pre-monsoon weather could increase dengue transmission in Kerala.

Climate change and warming weather could be worsening Kerala’s vector-borne disease burden, particularly dengue, a new study led by researchers at the Pune-based Indian Institute of Tropical Meteorology (IITM) found.

In the study, led by climate researcher Sophia Yacob and published in GeoHealth, researchers found that Kerala’s warm, humid climate already supports dengue transmission, and El Niño can intensify those conditions, especially before the monsoon, raising dengue risk during June–July.

El Niño years are periods marked by unusually warm sea-surface temperatures in the central and eastern equatorial Pacific.

They found that temperature, humidity, El Niño–Southern Oscillation (ENSO) conditions, rainfall, and the monsoon active and break phases are the primary climate indicators linked with dengue incidents in Kerala.

“Our study has found that there are many intricate and a combination of weather factors, observed both during the pre-monsoon and the monsoon seasons, that contribute to the dengue incidents reported in Kerala. Even within the state, there are regional-scale variations,” said Roxy Mathew Koll, who is the co-author of the study, told The Indian Express Wednesday.

“Kerala experienced humid and warm temperatures for long periods in the year. This means availability of favourable climatic conditions for higher transmission of dengue. El Niño–like conditions increase the dengue incidence, as it shifts large‐scale circulations toward warmer and drier pre‐monsoon conditions over the state,” Koll said.

The team deployed machine learning (ML) and developed a predictive dengue model using data from Kerala, but the scientists noted it can be extrapolated to similar vector-borne diseases and viral or seasonal influenza.

This model combines real-time climate forecasts and health surveillance, and can predict up to 72 per cent of the variation in dengue cases.

The pre-monsoon season (March to May) over Kerala is marked by both high temperatures, high humidity, and thunderstorms. Dengue cases in the state begin to rise in May and peak in June and July. Of all dengue cases annually reported in Kerala, nearly 60 per cent occur during the Southwest Monsoon season (June to September).

As the climatic signals arrive at different times, Kerala, researchers said, can be better prepared to tackle vector-borne diseases up to five months in advance.

But during El Niño years, like 2026, there is an added challenge: El Niño brings warmer pre-monsoon conditions over Kerala, which make it favourable for greater dengue risk during the monsoon.

The IITM team had previously studied dengue incidents in Pune city in Maharashtra and plans to soon extend studies on vector-borne disease-climate variations to Chennai and Bhopal.