wildlife epidemiologist christine johnson handicapped the stakes.the odds of another pandemic? >> i would say another pandemic is guaranteed. >> guaranteed? >> it's not a matter of if, but when. that's why we're so committed to preparation. >> johnson leads the uc davis team and has been hunting viruses around the globe for decades. we were headed to an abandoned mine shaft to look for bats. johnson told us bats are prime suspects for spillover. they harbor more viruses lethal to humans than any other mammal. new bat species and new viruss are still being discovered. it seems like a really daunting task for you to find pathogen x before it finds us. >> it's definitely achievable. >> it is achievable? >> absolutely. it's all here right now, right? it's not like we're exploring outer space. all of these viruses and all of the wildlife are right here on our planet. >> the bats would start flying at dusk. we waited as the uc davis team and their ugandan partners hung a fine mesh net across the entrance of the cave. we wore masks and goggles to protect o