Pune: El Niño-linked warming in Pacific Ocean could increase dengue risk in Kerala, a study led by Indian Institute of Tropical Meteorology (IITM), Pune, has found as a powerful El Niño develops. The study, researchers said, could offer health authorities an early warning system months before the outbreaks.Kerala is currently experiencing a severe dengue season, recording 7,188 confirmed cases between June and Aug, around 60% above the decade-long average for the same period, data from the Kerala directorate of health services has revealed.Published in GeoHealth journal on Wednesday, the study analysed 14 years of dengue and climate data from Kerala (2006-2019) and found a clear link between El Niño years and higher dengue incidence. The researchers said warmer Pacific waters were associated with warmer and relatively drier pre-monsoon conditions in Kerala, creating favourable conditions for mosquito breeding before dengue cases surged during the monsoon.The study was led by Sophia Yacob and Dr Roxy Mathew Koll of IITM, in collaboration with ICMR’s National Institute of Translational Virology and AIDS Research (ICMR-NITVAR) and Savitribai Phule Pune University. “In our model-based analysis, Kerala’s high dengue years coincided with El Niño, while mild dengue years fell in La Niña years,” Dr Koll said.To convert this climate link into a forecasting tool, the team developed a machine-learning model that explained 72% of monthly variations in dengue cases in Kerala. The model suggested climate-driven dengue cases could increase 16-20% by 2040, and by up to 113% by the end of the century under a high-emissions scenario.The findings build on the team’s earlier Pune-focused research, which projected dengue risk in the city could rise 13-112% under warming scenarios. Dr Koll, however, said El Niño had a weaker influence on Pune than on Kerala. “We found that the role of El Niño in dengue risk over Pune is weak, while local weather conditions play a major role. In Pune, a combination of temperatures above 27°C, moderate and evenly distributed rainfall, and humidity between 60% and 78% during the monsoon (June-Sept) increases dengue incidence,” he said.A key finding was that Pacific sea-surface temperatures showed their strongest correlation with Kerala dengue cases about three months in advance. “When humidity and temperature patterns are included, the lead time extends to nearly five months, enough to allow authorities to strengthen mosquito-control measures and prepare hospitals ahead of seasonal spikes,” Yacob said.The researchers cautioned that the study period ended in 2019 and therefore could not directly attribute Kerala’s current dengue season to the ongoing El Niño event. Instead, it highlighted a historical pattern that mirrored present conditions.The study also stresses that climate was only one part of the dengue equation. Factors like vector control, water storage practices, waste management, urbanisation and disease surveillance continued to play a critical role in determining outbreak severity.“Climate signals can give us a head start by several months,” Dr Koll said, adding, “Combined with health and mosquito surveillance, they can help us intensify vector control, prepare hospitals and reach vulnerable communities before the seasonal surge.”Co-author Dr Sreelakshmi PR, scientist at ICMR-NITVAR, said the findings underscored the need to integrate climate indicators into routine dengue surveillance, rather than relying solely on case counts.
