Pune, Sep 16 (PTI) Climate variables such as temperature, rainfall, humidity and El Nino conditions can help predict dengue risk months before cases of the mosquito-borne infection peak, a study focused on Kerala has found.
El Nino, which is marked by the unusual warming of surface waters in the tropical Pacific Ocean, brings warmer pre-monsoon conditions favourable for greater dengue risk, said the report published in the journal GeoHealth recently.
The findings also show how continued global warming could increase dengue risk in the future.
Researchers of the Indian Institute of Tropical Meteorology (IITM) and National Institute of Translational Virology and AIDS Research (NITVAR) studied dengue cases in Kerala.
The southern state reported 7,188 confirmed cases during June- August 2026, 60 per cent above the average for the same period during 2016 to 2025, and more than five times the average during 2006 to 2015.
The study found that Kerala’s dengue risk begins to take shape months before cases rise. Temperature and humidity before the monsoon, El Nino conditions over the Pacific, and rainfall during the monsoon can together provide warning signals up to five months in advance.
The study led by Sophia Yacob and Roxy Mathew Koll at the IITM analysed 14 years of monthly dengue and climate data for Kerala. The research was carried out with collaborators from ICMR-NITVAR in Pune, Kerala University of Health Sciences in Thiruvananthapuram and Government Medical College in Thrissur.
Dengue cases in Kerala generally begin rising in May and peak during June and July, the study found. Nearly 60 per cent of the reported cases occured during the Southwest Monsoon. The climatic signals arrived at different times.
“Humidity and the difference between day- and night-time temperatures can provide indications up to five months ahead. Temperature and El Nino conditions provide two to three months of lead time, while monsoon rainfall acts as an immediate signal,” the study said.
The researchers found that pre-monsoon maximum temperatures of about 30.5 to 32.5 degrees Celsius, combined with moderate humidity of 66 to 79 per cent followed by moderately high monsoon rainfall of around 180 to 450 mm per month, were associated with higher dengue incidence.
“El Nino adds another early signal by bringing warmer pre-monsoon conditions over Kerala favourable for greater dengue risk during the monsoon. At the other extreme, very heavy rainfall may temporarily reduce transmission by flushing out mosquito eggs and larvae,” the study said.
Using these climate signals, the researchers developed a machine-learning model that could predict 72 per cent of the variation in dengue incidence.
Combined with real-time climate forecasts and health surveillance, it could serve as an early-warning tool for Kerala’s health department, the study said.
Climate alone, however, does not explain the variations in dengue incidence.
Urbanisation, water storage, waste management, vector control, circulating virus strains, immunity and disease surveillance also influence the dengue variations, the study observed.
“The model we developed can be adapted to other regions, providing a valuable tool for managing climate-sensitive diseases like dengue,” Yacob said.
Sreelakshmi P R of the ICMR-NITVAR said this study shows how climate variables can help anticipate dengue risk months before cases peak.
“It is a call for routine surveillance to move beyond dengue case counts alone and step up to integrated surveillance that includes region-specific climate signals,” Sreelakshmi said.
The study projects that climate-driven dengue incidence for Kerala could rise by 16-20 per cent during 2021 to 2040 compared with the recent past. By the end of the century, the increase ranges from 46 per cent under low emissions to 113 per cent under a very high-emissions pathway.
Roxy Mathew Koll said, “Climate signals can give us a head start by several months. Combined with health and mosquito surveillance, they can help us intensify vector control, prepare hospitals and reach vulnerable communities before the seasonal surge.
“We have the potential to develop similar locally calibrated disease prediction systems for other states. This requires reliable health data combined with local climate and mosquito surveillance,” Koll said. PTI PR KRK
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