Scientists at Georgetown University have described in Nature a link between climate change and viral transmission that poses the extension of future pandemics due to global warming.
As Earth’s climate continues to warm, researchers predict that wild animals will be forced to relocate their habitatslikely to regions with large human populations, which will dramatically increase the risk of a viral jump to humans that could lead to the next pandemic.
In their study, the scientists made the first comprehensive assessment of how climate change will restructure the global virome of mammals. The work focuses on geographic range changes: the journeys species will take as they follow their habitats into new areas. When they meet other mammals for the first time, the study projects that they will share thousands of viruses.
They say these changes provide greater opportunities for viruses like Ebola or coronaviruses to emerge in new areas, making them harder to track, and in new types of animals, making it easier for viruses to jump through a kind of "trampoline" towards humans.
"The closest analogy is actually the risks we see in the wildlife trade"The study’s lead author, Colin Carlson, a research assistant professor in the Center for Global Health Science and Security at Georgetown University Medical Center, says in a statement. "We care about markets because bringing sick animals together in unnatural combinations creates opportunities for this gradual process of emergence, like how SARS jumped from bats to civets, then from civets to people. But markets are no longer special; in a changing climate, that kind of process will be the reality in nature almost everywhere".
It is worrying that the habitats of animals move disproportionately in the same places as human settlements, creating new hotspots of indirect risk. Much of this process may already be underway in today’s 1.2 degree warmer world, and efforts to reduce greenhouse gas emissions may not prevent these events from unfolding.
Another important finding is the impact that rising temperatures will have on bats, which account for the majority of the new shared viruses. Their ability to fly will allow them to travel long distances and share most viruses. Due to its central role in viral emergence, the greatest impacts are projected in Southeast Asia, a global hotspot for bat diversity.
"at every step"Carlson said, "our simulations have taken us by surprise. We spent years double-checking those results, with different data and different assumptions, but the models always lead us to these conclusions. It’s a really amazing example of how well we can actually predict the future if we try.".
As viruses begin to jump between host species at an unprecedented rate, the authors say impacts on conservation and human health could be impressive.
"This mechanism adds another layer to how climate change will threaten human and animal health."says study co-senior author Gregory Albery, a postdoctoral fellow in the Department of Biology at Georgetown University’s College of Arts and Sciences.
"Exactly how these new viruses might affect the species involved is unclear, but it is likely that many of them translate into new conservation risks and fuel new outbreaks in humans.".
Taken together, the study suggests that changing climate will become the greatest risk factor in origin for the appearance of diseases, overcoming higher-profile problems like deforestation, the wildlife trade, and industrial agriculture. The authors say the solution is to pair wildlife disease surveillance with real-time studies of environmental change.
"When a Brazilian free-tailed bat makes its way to Appalachia, we should invest in knowing what viruses accompany it"Carlson says. "Trying to detect these jumps in real time is the only way we can prevent this process from leading to more infections and more pandemics.".
"We are closer than ever to predicting and preventing the next pandemic"Carlson says. "This is a big step towards prediction; now we have to start working on the hardest half of the problem".