Researchers Are Working to Predict the Next Animal-Borne Pandemic

You've probably heard about outbreaks of Ebola, Lassa fever, and Zika virus around the world in recent years. Before producing epidemics or pandemics, the pathogens that caused the diseases had to "spillover" from wildlife to humans.

When a virus or another infectious agent makes the jump from animals to humans, it's called a zoonotic disease or zoonosis. A zoonotic disease you've probably heard about recently is SARS-CoV-2, the virus that causes COVID-19.

Assessing New Viruses

COVID-19 has put infectious disease experts around the world on an even higher alert for the potential next pandemic. To aid in making predictions, researchers have created an online tool that can help others evaluate the risk of a new virus jumping (or "spilling over") from animals into humans.

The tool is called SpillOver: Viral Risk Ranking and it was sponsored by the U.S. Agency for International Development (USAID), the PREDICT project, the Global Virome Project, and the One Health Institute at UC Davis.

The online application is meant to help researchers and governments assess the risk of new viruses as they are discovered and communicate that risk to ensure that disease prioritization, prevention, and control actions are taken.

How the Tool Works

The tool evaluates a newly-discovered virus and based on the findings, creates a list of other viruses that policymakers and public health officials might want to keep an eye on.

SpillOver is designed for viruses that originate in mammals, reptiles, amphibia, and birds, as well as those in the many families of viruses that are of concern to human health. The application's design was based on a credit reporting system that is used by bankers, and it can be updated to include new data and risk factors.

In an article describing the tool, the authors—who are from UC Davis, the Mailman School of Public Health at Columbia University, the Smithsonian Conservation Biology Institute, the Wildlife Conservation Society, the EcoHealth Alliance, and Metabiota, Inc.—stated that “we now live in an era in which threats posed by viral pandemics are a daily reality. A single lethal virus can emerge suddenly and spread rapidly to every household and every community without regard to national borders or to social and economic standing."

Jonna Mazet, DVM, PhD, a professor of epidemiology and disease ecology at the University of California at Davis School of Veterinary Medicine and an author of the study introducing SpillOver, tells Verywell that because the tool is open-source, it means that researchers from around the world—including epidemiologists, wildlife veterinarians, and experts from other disciplines—will be able to crowdsource the science and contribute by adding information about new viruses as they are found.

Identifying Risk Factors

To create the SpillOver application, the authors identified risk factors of the viruses, hosts, and the environment that would be most relevant to animal viruses spilling over into humans.

The risk factors included in the assessment tool were the number of animal hosts, where they are found geographically, and the types of environments in which they live.

The researchers then ranked the risk of 887 wildlife viruses using available data that was collected by the USAID Emerging Pandemic Threats PREDICT project.

The Lassa virus took first place, with SARS-CoV-2 coming in second. Even though it caused a pandemic, SARS-CoV-2 did not make first place because not much was known about its animal hosts.

The larger list of viruses included several newly-discovered coronaviruses that are considered high risk for moving from wildlife to humans.

Why Do Viruses Make the Jump?

Mazet says that viruses are jumping between wildlife and humans at a faster rate because humans are moving into wilderness areas at a faster rate. Usually, when humans move into wilderness areas and other isolated locations, it's because they are looking for raw materials like the rare metals needed for technology such as cell phones or to open up more land for agriculture.

“It’s not the wildlife, or even the viruses, that are jumping out and attacking or infecting us—it's our behavior that puts us at risk. And that's sometimes a bitter pill to take to recognize that,” Mazet says. “But on the other hand, that means it is within our capacity to adjust our behavior so that we reduce our risk.”

As people move into areas that were once isolated, they often bring domesticated animals with them. Viruses are then able to jump to livestock and eventually move to humans. “That provides for another opportunity for a pathogen to change and become a bit more virulent before it spills over into people,” Mazet says.

Although the SpillOver tool is for assessing viral zoonoses, there is also a risk of disease and epidemics from bacteria that can spread from animals to humans. In bacteria, Mazet says that the risk is not so much from a bacterium jumping from animal to human as it is from the genes for antimicrobial resistance spreading.

Watching For the Next Virus

“This tool is very much about understanding a yet-unknown virus—aka virus X—that can crop up at any time," says Sarah Olson, PhD, an author of the study and the associate director of epidemiology at the Wildlife Conservation Society in the Bronx, tells Verywell. "The tool is useful to rank viruses ‘known to science’ but its other value is pointing out a list of information that is needed to improve our assessment of risk.”

According to Olsen, there are an estimated 1.67 million undescribed viruses in mammals and birds. About half of those are thought to be capable of spilling over into humans. “To put it another way, scientists have only cataloged about 0.2% of global virus diversity in mammals and birds," Olson says.

Mazet says that “we need to know: how and why does a wildlife virus become zoonotic? Which viruses pose the greatest threat?”

The Threat of Coronaviruses

According to Mazet, the journal article on the SpillOver tool was mostly written before SARS-CoV-2 was fully recognized. Olson points out that the virus was not detected in wildlife before the pandemic and was already spreading globally before the threat was fully recognized. 

The study authors noted that many coronaviruses may spill over into humans but go unrecognized. A lack of diagnostic capabilities and poor reporting contribute to them being overlooked. Additionally, the viruses usually only cause mild symptoms—or no symptoms at all—making them even harder to spot.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.