New study finds concerning factor driving increase in dangerous disease: 'Worst year ... on record'

Warmer temperatures and a variation in the length of dry seasons appear to be influencing the prevalence of dengue fever, according to a new study.

What's happening?

Scientists looked at temperature and rainfall trends in the Philippines to see if there was a connection with dengue fever risks. Mongabay summarized the study, which found that temperature increases went hand in hand with increased dengue incidence throughout each of the 16 regions studied.

However, the effects of rainfall were less clear-cut. In regions with relatively stable dry season lengths, rainfall helped to flush out stagnant water, which tends to reduce mosquito breeding sites and makes dengue transmission less likely. However, sporadic rainfall in regions with less predictable dry seasons resulted in weaker flushing, creating opportunities for the formation of new water pools that can serve as breeding sites.

The researchers found similar results using data from Puerto Rico.

Why is this study important?

This study "represents a significant step toward understanding how climate change may impact mosquito-borne diseases globally," lead author Olive R. Cawiding said in a statement.

A number of studies have indicated that a warming world is driving an increase in mosquito populations and expanding their ranges, which can drive the spread of vector-borne diseases like dengue, malaria, Zika, and West Nile virus. For instance, one recent study found that several mosquito species populations are set to expand their ranges in North and South America in the coming years, thanks to warmer temperatures.

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Already, the World Mosquito Program called 2024 the "worst year for dengue cases on record." According to the Mayo Clinic, this vector-borne disease causes symptoms like a high fever, headache, muscle, bone or joint pain, nausea, vomiting, pain behind the eyes, swollen glands, and rash.

What's being done about vector-borne diseases?

As the threat of mosquito-borne diseases continues to rise, governments are looking for ways to zap out these blood suckers. For instance, San Diego County quickly sprayed for mosquitoes after confronting its first-ever locally acquired case of dengue in the fall of 2024. And officials in one Florida county are using X-rays to kill invasive mosquitoes there.

Meanwhile, scientists are also working on vaccines to protect people from malaria, a mosquito-borne disease that kills more than 400,000 people globally each year, per the Mayo Clinic. For example, a $70 million pilot program that tested one malaria vaccine in Africa helped reduce deaths among young children by 13% over a period of four years.

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