When an idea goes viral, it spreads like a disease. When a sickness goes viral, all of us are at risk. Whether it starts with animals, humans or bombs, how can we improve our chances of surviving the next global pandemic? At the Centers for Disease Control headquarters in Atlanta, a researcher studies mosquitoes (the world’s most dangerous animals) by letting them suck blood from his arms. Starting in the Hong Kong hotel where SARS turned into an epidemic, we trace how the disease spread worldwide. In a top secret U.S. government lab in Los Alamos, New Mexico, researchers track biological weapons around the world and map their potential impact.