Nature-based or man-made? Unraveling the debate over the origins of COVID-19

The debate over the origins of the COVID-19 virus has sparked a political firestorm in the U.S. and threatened the already fraught ties between Washington and Beijing.

An accidental lab-leak, or the dark side of mother nature? That fundamental question -- about the origins of a COVID-19 pandemic that has taken nearly 4 million lives -- has sparked a political firestorm in the U.S. and threatened the already fraught ties between Washington and Beijing. So far, multiple investigations have yielded few definitive conclusions. And as infection rates and deaths tail off in many developed countries, the Chinese government's perceived lack of cooperation into those investigations has prompted some of the world's leading virologists to reconsider the possibility that this pandemic could have been caused by a lab accident. In the early days of the pandemic, experts largely felt that the most likely explanation was that the virus jumped directly from animals to humans -- like all other pandemics and epidemics have in the past. Attention turned to a closely quartered wet-market in the central Chinese hub of Wuhan, freshly scrutinized for the exotic wild fare, which offered ample opportunity for an intermediary host. But while environmental samples from the market came back positive for the virus, animal samples that were tested ultimately did not.