Climate Change Set To Increase Dengue Death Toll, Warn Indian Scientists In New Study

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Oindrila Mukherjee

Last Updated:January 21, 2025, 19:01 IST

Dengue is strongly influenced by changes in meteorological conditions and, hence, the study investigated how changing monsoon patterns have altered its prevalence in Pune, a hotspot for the disease in India

The new study said India is likely to contribute to a third of the annual 100 to 400 million dengue infections. (Image: AFP/File)

Extreme weather events notwithstanding, climate change-driven warming is projected to increase the global burden of dengue with India contributing to a third of the annual 100 to 400 million infections, warned a new study by Indian scientists.

One of the world’s most widespread and rapidly increasing vector-borne diseases, dengue is strongly influenced by changes in meteorological conditions. The new study – published in the peer-reviewed scientific journal, Scientific Reports – investigated how changing monsoon patterns have altered the prevalence of the disease in Pune, which is a dengue hotspot in India.

The team led by researchers from Indian Institute of Tropical Meteorology (IITM), Pune, showed that heavy rains above 150 mm in a week reduce dengue prevalence by flushing out mosquito eggs and larvae. But, moderate rains spread over the monsoon lead to an increase in dengue mortality, indicating the links between the disease and changing monsoon variability due to warming.

“Our findings suggest that it is not the cumulative amount of rainfall, but rather the pattern of rainfall, that plays a crucial role in influencing dengue transmission in Pune," the research team said.

The years with higher dengue mortality rates in Pune witnessed temperatures ranging from 27 degrees Celsius to 35 degrees Celsius, as well as evenly distributed rains and relative humidity levels between 60 per cent and 78 per cent during the southwest monsoon season (June to September).

The infections are low from December to May, but begin to rise after the onset of the summer monsoon in June and peak in November. The analysis further showed that Pune recorded the highest number of dengue mortalities in 2014 during the study period (2004 to 2015) with a total 81 deaths.

“In a changing climate, dengue-related mortality in Pune is projected to rise by 13% in the near future (2021-2040), 23%-40% in the mid-century (2041-2060), and 30%-112% in the late century (2081-2100) under low-to-high emission pathways in response to the associated increase in temperature and changes in monsoon rainfall patterns," the study stated in its conclusion.

NEED TO DEVELOP EARLY-WARNING SYSTEMS

The scientists have also developed a machine-learning model based to predict dengue outbreaks with over two months’ lead time, which can help local authorities improve preparedness and reduce deaths.

“The study explains how climate impacts health. The model we developed can be adapted to other regions, providing a valuable tool for managing climate-sensitive diseases like dengue," said lead author Sophia Yacob from IITM Pune.

But, they also insisted that more cooperation from various health departments is urgently needed to develop customised early-warning systems for dengue, malaria and chikungunya for each city or district in India.

“We were able to conduct this study and prepare an early warning system using health data shared by Pune’s health department", said co-author Dr Roxy Mathew Koll. “We have meteorological data readily available from the IMD (India Meteorological Department), but cooperation from health departments is key to saving lives."

The findings are concerning, especially because there is enough evidence to show that monsoon rains are set to get more erratic in India as temperatures and humidity levels are expected to surge.