Animal relocating could be the trigger for the next pandemic, study finds

Efforts to reduce greenhouse gases may not stop it from unfolding.
Deena Theresa
The ability of bats to fly will allow them to travel long distances, and share the most viruses.CraigRJD/iStock

While we're dealing with the current COVID-19 pandemic, scientists have already predicted the whereabouts of the next pandemic.

An international research team led by scientists at Georgetown University published their findings in an article titled 'Climate change increases cross-species viral transmission risk' in Nature.

According to the study, climate change will become the most significant crucial risk factor for disease emergence, exceeding issues like deforestation, wildlife trade, and industrial agriculture.

But how?

The majority of emerging disease events over the past decades, such as SARS, Ebola, Zika, and the current COVID-19 pandemic, have been caused by zoonotic viruses and bacteria, showing how a virus jumps from animals to humans can have significant repercussions.

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As the Earth's climate continues to warm, researchers predict that wild animals will be forced to relocate their habitats to regions with large human populations, increasing the risk of a 'viral jump' to humans that could result in the next pandemic. 

Animals, a "stepping stone" species for viruses

The study assesses how climate change will restructure the global mammalian virome and focuses on geographic range shifts - species' journeys as they relocate to newer habitats. As they encounter other mammals for the first time, the study states that they will share thousands of viruses.

These shifts could bring numerous opportunities for viruses like Ebola or coronaviruses to crop up in new areas and into new types of animals, making it harder to track and easier for viruses to jump across a “stepping stone” species into humans.

“The closest analogy is actually the risks we see in the wildlife trade,” Colin Carlson, Ph.D., an assistant research professor at the Center for Global Health Science and Security at Georgetown University Medical Center, the study’s lead author said.

“We worry about markets because bringing unhealthy animals together in unnatural combinations creates opportunities for this stepwise process of emergence - like how SARS jumped from bats to civets, then civets to people. But markets aren’t special anymore; in a changing climate, that kind of process will be the reality in nature just about everywhere," he continued.

Animal habitats will move disproportionately in the same areas as human settlements, creating new hotspots of spillover risk. What's dismal is that much of this process could already be underway in today's warmer world. Efforts to reduce greenhouse gases may not stop these events from happening.

The threat of climate change to human and animal health

Bats, which are reservoirs for the majority of novel viral sharing, could be significantly impacted by rising temperatures. Their ability to fly will help them to travel long distances, and share more viruses. And because of their primary role in viral emergence, southeast Asia, a global hotspot of bat diversity, could be affected the most. 

“At every step,” said Carlson, “our simulations have taken us by surprise. We’ve 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 stunning example of just how well we can, actually, predict the future if we try.”

When viruses begin to jump between host species at unusual rates, the impacts on conservation and human health could be stunning. 

“This mechanism adds yet another layer to how climate change will threaten human and animal health,” Gregory Albery, Ph.D., a postdoctoral fellow in the Department of Biology in the Georgetown University College of Arts and Sciences, the study’s co-lead author said.

“It’s unclear exactly how these new viruses might affect the species involved, but it’s likely that many of them will translate to new conservation risks and fuel the emergence of novel outbreaks in humans.”

A 'big step towards prediction'

According to the authors, the solution is to pair wildlife disease surveillance with real-time environmental change studies. 

“When a Brazilian free-tailed bat makes it all the way to Appalachia, we should be invested in knowing what viruses are tagging along,” said Carlson. “Trying to spot these host jumps in real-time is the only way we’ll be able to prevent this process from leading to more spillovers and more pandemics.”