William Brangham:
Judy, trying to understand COVID's origins has been a complicated and politically fraught undertaking for almost three years now.
The Chinese government has been accused of impeding a full investigation. But this new research attempts to get the clearest picture to date.
And I'm joined by one of its authors. Angela Rasmussen is a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan.
Dr. Rasmussen, great to have you back on the "NewsHour."
So, the — at the beginning of the pandemic, a lot of attention was focused on this live animal market. And you and several of your colleagues, including Michael Worobey, have got some pretty strong evidence in your paper that indicates this was the epicenter of the outbreak.
What is that evidence?
Angela Rasmussen, University of Saskatchewan: We plotted all of the early cases from December of 2019 on a map of Wuhan, whether they were associated with the Huanan market or not, and many of them were.
This was identified as a place that was important early on in the outbreak investigation. We found that, whether those cases were associated with the market or not, whether they had been to the market or not, they really clustered around the market and formed almost a circle around the market, where the market was in the dead center.
Another piece of evidence is that we know that live animals, including some that were susceptible to SARS-Coronavirus-2 to infection, were being sold at the Huanan market, including in November and December of 2019. And, furthermore, there were environmental samples collected from the site of the market where these animals were sold that were positive for SARS-Coronavirus-2.
That really strongly indicates that those samples, those environmental samples, may have come from the animals. And on top of that, those samples were often collected from things associated with animals, such as cages, hair and feather removal devices, and carts.
And then, finally, there were actually two different genetic varieties, or variants, of SARS-Coronavirus-2 that were at the market, lineage A and lineage B. Initially, we thought that lineage B was spreading at the market, but we didn't understand that lineage A was also there, until it was found in an environmental sample.
This suggests that really there had to be two separate introductions into the market. And the only thing that explains this is two people independently coming into the market and being infected with lineage B and lineage A about a week apart.
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