A warming world gives viruses more chances to hitchhike from species to species

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Climate change is pushing mammals into new territory, increasing the number of opportunities for viruses to jump from species to species. There could be 15,000 new cross-species if global temperatures continue to rise as predicted, according to new research published today in the journal Nature.

Most of the virus species in mammals capable of infecting humans are only found in the wild. The worry is that more of the viruses could make the leap to humans and cause a health crisis.

Gregory Albery, a disease ecologist at Georgetown University and co-lead author of the study, said in "This work provides us with more incontrovertible evidence that the coming decades will not only be hotter but sicker."

Many species might need to migrate because the climate they are used to living in is changing. It is possible that places that used to be inhospitable are becoming more attractive. They bring diseases with them when they travel. Viruses have more hosts with whom they can hitch a ride. That allows viruses to reach places that they wouldn't have been able to in the past.

Albery said that the process has been taking place mostly unobserved and below the surface.

A spillover event is when a virus passes from one species to another. A zoonotic disease can emerge if there is a spillover between an animal and a human. The zoonotic virus that causes COVID-19 can move between humans and other animals. There is evidence that the novel coronaviruses came from bats. It jumped to at least one other animal before reaching humans.

A new study looked at the geographical ranges of over 3000 mammal species in a warming world. They took into account how land use might change.

There could be over 300,000 first encounters between different kinds of animals in a future with two degrees of global warming. Most of those encounters would be in Asia and Africa. That could lead to 15,000 transmission events in which at least one novel virus moves from one species to another. Bats are unique among mammals because they can fly from continent to continent.

The researchers don't know how often the viruses will hop over to humans. Not every virus that comes from an animal to a human causes an epidemic. Albery noted on the call that when a virus jumps to a new species, it can create conditions that might help the virus evolve into one that can jump into humans.

The raccoons can thrive in forests, marshes, suburbs, and city centers. It is possible that a new virus could be brought into places where humans live if the raccoons suddenly become susceptible to it. The virus has shown that it is prone to jumping between species, since it has already made one leap from another animal to a raccoon.

The paper suggests that these trends are already underway and will be a problem even under some of the best-case scenarios for future climate change. The world has already warmed by over one degree, and we are well on our way to surpass that two-degree threshold.

The authors say that the urgent need to prepare for more spillover is due to the emergence of the COVID-19 pandemic shortly after this research was completed. We need to build health systems that are ready for that.

The authors say that includes pairs of new viruses with observations of how species are changing. It is part of a bigger movement to adopt a concept called One Health, which acknowledges that the health of animals, people, and the environment are all connected.