How does climate change influence the development of infectious diseases?

Scientists from the University of Hawaii, Munnoa, scanned some 77,000 publications to select 830 that address climatic events (heat waves, floods, etc.) having an impact on infectious diseases (malaria, dengue fever, etc.) . The results of their research have been published on the nature.com site, where they explain to begin with that 58% of the diseases with which humanity is confronted can be aggravated by climatic hazards.

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Human pathogenic diseases and transmission pathways compounded by climate hazards are too numerous for comprehensive societal adaptations,” the report reads. It is therefore essential to work on reducing greenhouse gas emissions, in order to work on this problem.

Several factors involved

The emergence of a human disease due to a pathogenic agent such as a bacterium or a virus is influenced by biological, but also ecological, environmental and social factors. Climate change has, for example, allowed the expansion into new territories of mosquitoes, ticks, fleas, birds, and other mammals that have been implicated in epidemics.

In other places on the planet, global warming has allowed viruses to survive the winter. Drought, on the other hand, forces some animals to move and causes the concentration of mosquitoes and birds around water points, which facilitates the transmission of a virus. In the same vein, the heat brings the world’s population together to meet in places where they bathe, for example. And as for floods, they are associated with sewage overflows, which also cause a greater spread of viruses.

Not always worse

But they also note that, conversely, 16% of them have decreased following these hazards. The researchers explain that while “the vast majority of diseases have been aggravated by climatic hazards, some have been reduced”. This is how 63 diseases, including influenza, SARS and Covid-19, did not spread more because of climatic hazards, which is explained by “
inappropriate conditions for the virus or due to a stronger immune system in warmer conditions”.