The novel coronavirus SARS-CoV-2 is the latest pathogen to “spill over” from animals to people, but hundreds of thousands of other viruses lurking in animals could pose a similar threat. Now, a new online tool ranks viruses by their potential to hop from animals to people and cause pandemics.

The tool, called SpillOver, essentially creates a “watch list” of newly discovered animal viruses that pose the greatest threat to human health. The researchers hope their open-access tool can be used by other scientists, policymakers and public health officials to prioritize viruses for further study, surveillance and risk-reducing activities, such as possibly developing vaccines or therapeutics before a disease spills over.