Climate change is pushing mammals into new territory, increasing the number of opportunities for viruses to jump from species to species, including humans. If global temperatures continue to rise as predicted, there could be a total of 15,000 new ‘viral sharing events’ between species by 2070, new researchers say. Research published today in the magazine Nature†
From the least 10,000 virus strains among mammals that can infect humans, most still only circulate among wildlife. The concern is that more of those viruses could eventually make the leap to humans, possibly causes a health crisis like the COVID-19 pandemic.
“Ultimately, this work provides us with more incontrovertible evidence that the coming decades will not only be hotter, but also sicker,” Gregory Albery, a disease ecologist at Georgetown University and co-lead author of the study, said in an interview with reporters.
As global temperatures rise, many species may need to migrate as the climate they are used to living in is changing. Others may find that places that were once inhospitable—perhaps they were too cold—are becoming more and more alluring. As they travel, they carry pathogens with them. Essentially, viruses now have more hosts that allow them to hitchhike long distances. This allows viruses to reach places and species they would not otherwise have had access to.
“Even now, this process is probably happening, mostly undetected and below the surface, and we need to start looking for it,” Albery said.
When a virus passes from one species to another, this is called a “spillover” event. If spillover occurs between an animal and a human, a zoonosis can develop. The virus that causes COVID-19 is a zoonotic virus, meaning it can move between humans and other animals. there is proof the new coronavirus originated in bats. But it is likely jumped to at least one other animal before they reach humans.
The authors of the new study looked at possible changes in the geographic range of more than 3,000 mammal species in a warming world. They also took into account how land use might change, for example through deforestation and urban development.
According to the research, in a future with two degrees of warming above pre-industrial levels, there could be more than 300,000 “first encounters” between different species of animals. Most of those encounters would likely take place in tropical Asia and Africa. And that could lead to 15,000 transmission events with at least one new virus going from one species to another. A majority of the expected viral exchange involves bats, which are unique among mammals in that they can fly from continent to continent.
The researchers do not estimate how often viruses can then transfer to humans. And not every virus that makes its way from animals to humans causes an epidemic. But Albery noted in the press call that when a virus jumps to a new species, it can create conditions that could help the virus evolve into a virus that is “particularly well-suited or well-placed to make the jump to humans.”
To take raccoons, which can thrive in forests, swamps, suburbs and city centers. If those resourceful raccoons suddenly become susceptible to a new virus, they might be much more capable of taking that virus to places where people live. And since the virus has already jumped from another species of animal to a raccoon, the virus has shown a tendency to jump between species.
The new paper suggests that these trends are already underway and will pose a problem even in some of the best-case scenarios for future climate change. Goods well on your way toward crossing that two-degree threshold; the world has already warmed by more than a degree.
The COVID-19 pandemic emerged shortly after this study was completed, indicating the urgent need to prepare for more spillovers, the authors say. “We need to take that seriously as a real-time threat,” Georgetown University biologist Colin Carlson, another lead author of the study, said on the call. “We must recognize that climate change will be the biggest upstream cause of disease onset. And we need to build healthcare systems that are ready for that.”
That includes linking surveillance of new viruses to observations of how species’ geographic ranges are shifting, the authors say. It’s part of a larger movement to adopt a concept called a healthwhich recognizes that animal health, people and the environment are all interconnected.
SOURCE – www.theverge.com