Higher global temperatures could trigger more disease outbreaks

OneAs global temperatures have increased in recent decades, the number of outbreaks of infectious diseases has also increased. SARS, MERS, Zika, West Nile, COVID-19, and now clusters monkey pox and polio recently threaten public health.

That is not random. In one research published in August in Natural climate change, researchers have been trying to understand the relationship between major environmental changes associated with higher greenhouse gas emissions – including global warming, sea level rise, hurricanes, floods floods, droughts and heat waves – and outbreaks of 375 human infectious diseases caused by viruses, bacteria, and other pathogens. They found that 58% of these public health threats are driven by climate change.

“The health impacts of climate change are here to stay,” said Dr Vishnu Laalitha Surapaneni, assistant professor of medicine at the University of Minnesota. “And they’re affecting us right here, right now.”

Scientists say viruses and other pathogens do not get better at higher ambient temperatures. Instead, it is more likely that the hosts they infect are affected by climate change. For example, rising global temperatures mean that the geographic range of many disease-carrying animals – including insects like mosquitoes – is expanding rapidly. “As they move around in search of better climates, there’s more opportunity for the virus to spread to other animals that can be found,” said Gigi Gronvall, senior scholar at the Johns Hopkins Center for Health Security. other mammals, and then from some of those mammals to humans,” said Gigi Gronvall, senior scholar at the Johns Hopkins Center for Health Security at the Bloomberg School of Public Health. In the same way that highways, planes, and trains connect remote parts of the world, these animals are transporting their microbial masses to new places.

Tick ​​disease is one of the examples of climate impacts on human health. With temperatures warming, tick habitats are stretching further north, into Canada and even Nova Scotia. No case has been reported anywhere Lyme diseasecarried by ticks, until 2002.

Read more: Nearly 15% of people worldwide have had Lyme disease, study says

Warm ocean water also allows dangerous pathogens to thrive, including flesh-eating bacteria of the genus vibrio. Infections from these bacteria have been on the rise lately — not only when natural climate disasters like hurricanes sweep over land and bring contaminated water into closer contact with people, but also when people have a cut or wound in contact with the ocean, which has become fertile water for bacteria growth. In one report published by Lancet In 2021, a team of health and climate experts from 43 academia and United Nations agencies analyzed data on the impact of the environment on human health, including the role of climate change. role of pathogens. The number of coastlines on which Vibrio bacteria grow has now increased by 25% in the northeastern United States and by 4% in the Pacific Northwest.

With global warming, mosquitoes are also invading further north than they have ever ventured before. The diseases they carry, such as dengue, have been reported outside of their typical tropics in places like New York City — and worryingly, cases are not always also from tourists, which are usually from infected mosquitoes circulating in the area. Other pathogens carried by these insects, including those that cause Zika and yellow fever, are also being reported in parts of the world where they were not common before. The Lancet The report shows that in some low-income countries where mosquitoes are known to thrive, the amount of time the insect is active now has increased by 39% between 1950-1959 and 2010-2019.

Although mosquitoes typically thrive in wetter climates, hotter temperatures that lead to drought can also promote certain mosquito-borne diseases, such as West Nile disease. In drier conditions, birds — one of the vectors of mosquito transmission — tend to congregate in places where water is scarce, creating ideal conditions for mosquitoes to find new hosts.

Bats are also expanding into new territories as they cope with the stress of climate change. Warming temperatures cause them to seek out more suitable climates, and their increased mobility increases their chances of coming into contact with people and spreading diseases, such as coronavirus. “There’s a lot of mixing of animal populations that haven’t been mixed before,” says Gronvall.

Understanding these shifting behaviors and changing habitats requires an appreciation that the health of one species is closely tied to the health of all species. Scientists say it is important to devote more resources to understanding how viruses, bacteria and other pathogens circulate between different animal species to better understand how their behavior can affect how it affects human health. “It’s really hard to build bridges between different communities, like the US Centers for Disease Control and Prevention and the Environmental Protection Agency or the Department of Agriculture,” says Gronvall. “But we will need a much more integrated approach to address research questions that everyone agrees are important.”

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