A hotter world will likely be a sicker world.
The Earth’s rising temperature has obvious repercussions on human health, such as heat waves that are hotter than our physiology can tolerate. Humanity’s departure from the stable climate it inherited will bring surprises. Some of these may be existing diseases that emerge in new places or spread at a greater rate. Experts fear some may be entirely new diseases.
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The mosquito-borne infection malaria has killed more than half a million people each year over the past decade. Most of these victims were children, and almost all (95% in 2022) were in Africa.
As a source of disease, infectious mosquitoes can be predicted to need at least three things: warm temperatures, moist air, and puddles of water to breed. So what difference will global warming make?
Parasites on the march
“The relationship between climate and the spread of malaria is complex and has been the subject of intense study for nearly three decades,” say water and sanitation experts Mark Smith (University of Leeds) and Chris Thomas (University of Lincoln).
Read more: Mapping malaria in Africa: climate change study predicts where mosquitoes will breed in future
Most of this research has focused on sub-Saharan Africa, the global epicenter of malaria cases and deaths. Smith and Thomas combined temperature and water movement estimates to create a continent-wide malaria risk analysis.
The results showed that conditions for malaria transmission will become less favorable overall, especially in West Africa. But in the future, places where temperatures and humidity will be suitable for infectious mosquitoes will also be places where many more people are expected to live near rivers, such as the Nile in Egypt.
“This potentially means that the number of people living in malaria-endemic areas (suitable for transmission for more than nine months per year) will rise to over one billion by 2100,” they say.
Elsewhere, tropical diseases will lose their relevance as the insects that carry them survive farther from the equator. This is already happening in France, where dengue fever cases increased rapidly in the hot summer of 2022.
“Apparently the Veneto plains [in Italy] It emerges as an ideal living space for culex Mosquitoes can harbor and transmit West Nile virus,” adds Michael Head, senior research fellow in global health at the University of Southampton.
Read more: Dengue fever in France: Tropical diseases in Europe may not be so rare for much longer
Mark Booth, senior lecturer in parasite epidemiology at Newcastle University, says research suggests the global spread of mosquito-borne diseases such as malaria and dengue will change. That’s as clear a picture as Booth can get from modeling more than 20 tropical diseases in a warming world.
“For most other parasites there was little or no evidence. We don’t know what to expect,” he says.
Read more: Why is climate change making parasitic diseases harder to predict?
Some diseases will bring new torments to human-raised species. Bluetongue virus, a virus transmitted by sandflies, is expected to infect sheep farther away (in central Africa, western Russia and the United States) than in subtropical Asia and Africa, where it originated, Booth says.
The prognosis of some diseases affecting humans will also worsen. UCL academics neuroscientist Sanjay Sisodiya and earth system scientist Mark Maslin found that climate change exacerbates the symptoms of certain brain disorders.
Read more: Climate change linked to worsening brain diseases – new study
“Each of the billions of neurons in our brain is like a learning, adapting computer with many electrically active components,” they say. “Many of these components operate at different speeds depending on the ambient temperature and are designed to work together within a narrow temperature range.”
Sisodiya and Maslin say humans, a species that evolved in Africa, are comfortable between 20°C and 26°C and 20% to 80% humidity. Our brain is already operating close to the edge of its preferred temperature range in most cases, so even small increases matter.
“When these environmental conditions quickly shift to unusual ranges, as with extreme heat and humidity due to climate change, our brains have difficulty regulating our temperature and begin to malfunction.”
One planet, one health
Frankly, staying healthy isn’t as simple as regulating what you eat or how often you exercise. There are many things that are out of your immediate control.
“In less than three years, the World Health Organization (WHO) declared two public health emergencies of international concern: COVID-19 in February 2020 and monkeypox in July 2022,” said Arindam Basu, associate professor of epidemiology and environmental health. said. University of Canterbury.
“At the same time, extreme weather events are constantly reported around the world and are expected to become more frequent and intense. “These are not separate issues.”
Basu underlines the danger of new diseases emerging, especially from pathogens that can jump between humans and animals, as habitats change due to global warming.
Read more: One Health: Why we need to combine disease surveillance and climate modeling to prevent future epidemics
“As forests are cleared to make way for agriculture and the exotic animal trade continues, close contact between humans and wild animals is increasing,” he says. “At the same time, thawing permafrost exposes microbes hidden beneath the ice.”
Since pathogens share the same ecosystem with the humans and animals they infect, a new understanding of health is urgently needed. Basu says this should aim to optimize the health of people, wildlife and the environment.
Diseases. The climate crisis reveals once again our innumerable connections to everything else and our shared vulnerability on the only planet known to harbor life.
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