Print Did the global pandemic seep from a truckbed crowded with animal cages on its way to market? A cave where villagers dig bat guano? A mislabeled vial in a Chinese coronavirus lab? Those theories have spun into a blame game and a geopolitical battleground. But for scientists, finding the original source of SARS-CoV-2, the virus that causes COVID-19, is key to understanding how to predict, prevent and contain future pandemics that may arise, whether from a leak at one of a growing number of pathogen labs or the accelerating encroachment of humans on the natural world. Pinpointing the origin of a virus is critical to marshaling a quick response that could save lives and protect economies — especially in the early days of an outbreak. Evidence of a natural spillover would drive efforts to limit human interaction with wild animals and set up a stronger surveillance system. A lab origin would intensify demands for strict international standards for types of research and the conditions under which they should be done.