From Bats to Human Lungs, the Evolution of a Coronavirus | The New Yorker

Analyses of the sars-CoV-2 genome indicate a single spillover event, meaning the virus jumped only once from an animal to a person, which makes it likely that the virus was circulating among people before December. Unless more information about the animals at the Wuhan market is released, the transmission chain may never be clear. There are, however, numerous possibilities. A bat hunter or a wildlife trafficker might have brought the virus to the market. Pangolins happen to carry a coronavirus, which they might have picked up from bats years ago, and which is, in one crucial part of its genome, virtually identical to sars-CoV-2. But no one has yet found evidence that pangolins were at the Wuhan market, or even that venders there trafficked pangolins. “We’ve created circumstances in our world somehow that allows for these viruses, which would otherwise not be known to cause any problems, to get into human populations,” Mark Denison, the director of pediatric infectious diseases at Vanderbilt University Medical Center’s Institute for Infection, Immunology, and Inflammation, told me. “And this one happened to say, ‘I really like it here.’”