Climate change could be responsible for nearly one-fifth of the current dengue cases in the global population, with the potential to increase instances of the disease by an additional 40-60 per cent by 2050, according to a new study.

These findings, from researchers at Stanford and Harvard Universities, provide the most definitive evidence to date that climate change is a major factor driving the global surge in mosquito-borne diseases.

The study was presented at the Annual Meeting of the American Society of Tropical Medicine and Hygiene.

"We looked at data on dengue incidence and climate variation across 21 countries in Asia and the Americas and found that there is a clear and direct relationship between rising temperatures and rising infections," said senior author Erin Mordecai, an infectious disease ecologist at Stanford University.

"Our findings indicate that historical climate change has already increased dengue incidence by 18 per cent in the study region, and projections suggest a potential increase of 40 per cent to 60 per cent by mid-century, depending on the climate scenario, with some areas seeing increases of up to 200 per cent," the authors wrote.

According to the World Health Organisation, the increasingly warm and humid conditions driven by climate change are facilitating the spread of dengue, with new outbreaks reported in previously unaffected regions, including parts of Europe and the Eastern Mediterranean.

Countries in the Americas have recorded nearly 12 million cases of dengue in 2024, compared to 4.6 million in 2023, and locally acquired infections have been reported in California and Florida, the researchers noted.

The Asian countries studied included Vietnam and Cambodia, among others.

"It's evidence that climate change has already become a significant threat to human health, and for dengue in particular, our data suggests the impact could get much worse," Mordecai said.

The researchers also found that dengue-endemic areas now entering the 20-29°C "sweet spot for virus transmission"—such as parts of Peru, Mexico, Bolivia, and Brazil—could face the biggest future risks, with infections rising by 150-200 per cent over the next few decades.

However, areas already at the high end of the temperature range, like southern Vietnam, are likely to experience minimal additional climate impacts and may even see a slight decrease in cases, the authors added.

Overall, at least 257 million people are living in areas where climate change could double the incidence of dengue over the next 25 years, according to the analysis.

However, the study is likely to underestimate the actual threat posed by climate change to dengue transmission, as the researchers were unable to make projections for regions that have not consistently tracked infections, such as sub-Saharan Africa and South Asia.

The authors also suggested that cutting emissions to mitigate climate change could help reduce its effects on the spread of dengue.

They found that with sharp cuts in emissions, areas currently on track to experience a 60 per cent increase in dengue cases could instead see about a 40 per cent rise by 2050.

However, given that global climate models predict continued temperature rises even with emission reductions, the authors concluded that 17 of the 21 countries studied could still experience climate-driven increases in dengue, even under the most optimistic carbon-cutting scenarios.

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