When asked about the possibility of future pandemics,scientists say another one is coming and it's just a matter of when. In fact，there are about 1.7 million viruses（病毒）that are believed to exist in animals，and nearly half could potentially jump from animals to humans and kick off another pandemic. Finding ways to prevent that is the motivation driving a team of researchers at the University of California at Davis. They are trying to help the world's scientists determine how dangerous each virus might be by ranking its likelihood of being transmitted（传染）to humans and changing into a form that humans could easily pass to one another. The team has launched a web-based tool called SpillOver.It evaluates 32 risk factors to generate a risk score."We looked at viruses known to be transmissible from animals to humans and those that were newly discovered,"says Zoe Grange,who worked on the project as a wildlife disease scientist. By marking "high-risk"viruses, this publicly available database is intended to create a watchlist（观察名单）for scientists and policymakers. (78)Grange and her colleagues came up with the idea of a ranking tool in the spring of 2017.The Spillover database is designed so that researchers can add their own reports. They can add their virus discoveries and do their own rankings. (79) It's a tool everyone can use. Unlike other tools that evaluate the risk of a limited number of viruses, this database focuses on 887 viruses found in wildlife. SARS-CoV-2, which is the virus behind COVID-19, comes in second place for its likelihood to cause disease and spread within human populations.