: [POST-BROADCAST CORRECTION: The original audio version of this story misidentified the speakers of the last two quotes. The second to the last quote is from Kristian Andersen. The last quote is from Michael Worobey. The audio has been corrected.]
ARI SHAPIRO, HOST:
The debate about the origin of the pandemic still isn't over. A new analysis of data from the wet market in Wuhan, China, gives an inventory of what was there when COVID-19 first began spreading to people. There were humans, of course, animals, such as raccoon dogs, and the virus that causes COVID. The researchers say this genetic information is more evidence that the outbreak started at that market, but it seems unlikely to win over backers of an alternative theory that the virus leaked from a Wuhan lab. Reporter Gabriel Spitzer explains.
GABRIEL SPITZER, BYLINE: On the last day of 2019, with a mysterious new pneumonia flaring up around Wuhan, authorities shut down the Huanan seafood market. The next day, scientists from the Chinese CDC arrived with swabs and began collecting thousands of samples from surfaces. When Western scientists parsed the data from those samples, they found genetic evidence of animals known to be susceptible to COVID, like those raccoon dogs. And they found more, including the delicate RNA of the SARS-CoV-2 virus itself.
MICHAEL WOROBEY: It doesn't 100% prove that those animals had SARS-CoV-2.
SPITZER: Michael Worobey is an evolutionary biologist at the University of Arizona and a lead author on the paper.
WOROBEY: But you can just say goodbye to the idea that these animals weren't even there at the time the pandemic started. The ghosts of their DNA and RNA was certainly there.
SPITZER: The new analysis shows with unprecedented detail just where this stew of animal and viral genetic material turned up, right down to the individual market stall. Stall A, as it came to be called, was known as a place to buy exotic wildlife. This stall would emerge as a hot spot. Samples from the floor, the cages, a cart and the drain right outside showed that susceptible animals and the SARS-CoV-2 virus were there early in the outbreak. Other positive samples are clustered in the same area of the market. It's no smoking gun, says coauthor Kristian Andersen of the Scripps institute, but he says it tells a consistent story.
KRISTIAN ANDERSEN: All the evidence that we do have point to a very specific scenario, in fact, a very specific stall of which all of this could actually have started.
SPITZER: But skeptics at the new research say the underlying data is fatally flawed. Jamie Metzl, a fellow at the Atlantic Council and a leading proponent of the lab origin hypothesis, says the Chinese scientists focused their sampling on the corner of the market known for wildlife sales. So it's no surprise that that area had both more animals and more virus.
JAMIE METZL: These scientists are using what the scientists who collected the data have repeatedly said is a biased sample.
SPITZER: The study's authors say they statistically adjusted the data for sampling bias, and they say their work supports other lines of evidence pointing at the market. For example, the researchers used the slightly different lineages of virus found in the market samples to reconstruct its evolution. Andersen says when they compared that to virus from the broader pandemic, both family trees put the first spread around mid-November at the same place.
ANDERSEN: This is exactly what we would expect in a scenario in which all of this started at the market.
SPITZER: Worobey says the results point to a risk that public health experts have warned about for decades.
WOROBEY: The most likely origin of this pandemic was what we've always been concerned about in this field, which is taking these wild animals that harbor exotic viruses and placing them in the middle of the tinderbox of a big city.
SPITZER: The new findings are published in the journal Cell. For NPR News, I'm Gabriel Spitzer.
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