SARS-CoV-2 showed the world with devastating clarity the threat undetected viruses can pose to global public health. SpillOver, a new web application developed by scientists at the University of California, Davis, and contributed to by experts from all over the world, ranks the risk of wildlife-to-human spillover for newly discovered viruses.

Image/ Terra Kelly, UC Davis

SpillOver is the first open-source risk assessment tool that evaluates wildlife viruses to estimate their zoonotic spillover and pandemic potential. It effectively creates a watchlist of newly discovered viruses to help policymakers and health scientists prioritize them for further characterization, surveillance, and risk-reducing interventions.

The tool is linked to a study published in the journal PNAS, in which the authors identified the most relevant viral, host and environmental risk factors for virus spillover. Then the team ranked the risk from 887 wildlife viruses using data collected from a variety of sources, including viruses detected by the USAID Emerging Pandemic Threats PREDICT project, which UC Davis’ One Health Institute led from 2009 to 2020.

Coronaviruses rank high

Topping the list were 12 known human pathogens, which was expected and validates the tool’s utility. Interestingly, SpillOver ranked several newly discovered coronaviruses as higher risk for spillover than some viruses already known to be zoonotic. This watchlist includes a novel coronavirus provisionally named PREDICT_CoV-35, which ranked within the top 20.

The power of the tool lies in the fact that it is open-source — the more data entered, the more robust the ranking. SARS-CoV-2 currently ranks second out of the 887 viruses analyzed, between Lassa and Ebola viruses.

That may seem counterintuitive, the authors note, given the pandemic’s current global devastation. They explain that the tool is ranking the potential for another spillover beyond what has happened historically. In addition, key information remains undiscovered about SARS-CoV-2 and its spillover risk, such as the number and range of its host species. As scientists learn more about this virus, it is possible SARS-CoV-2 will move to No. 1.

“SARS-CoV-2 is just one example of many thousands of viruses out there that have the potential to spill over from animals to humans,” said lead author Zoë Grange, who led the development of SpillOver as a postdoctoral researcher with the UC Davis One Health Institute. “We need to not only identify but also prioritize viral threats with the greatest spillover risk before another devastating pandemic happens. Our SpillOver Viral Risk Ranking tool is the starting point for building proactive solutions.”

Read more at UC Davis