by An international team of virus experts said Thursday they had found genetic data from a market in Wuhan, China, linking the coronavirus with raccoon dogs for sale there, adding evidence to the case that the worst pandemic in a century may have been triggered by an infected animal that was being treated through the illegal wildlife trade.
The genetic data was taken from swabs taken in and around the Huanan Seafood Wholesale Market starting in January 2020, shortly after Chinese authorities shut down the market over suspicions it was linked to the outbreak of a new virus. By then, the animals had been cleaned up, but the researchers plugged walls, floors, wire cages and carts often used to transport animal cages.
In the samples that tested positive for the coronavirus, the international research team found genetic material belonging to animals, including large amounts that matched the raccoon dog, three scientists involved in the analysis said.
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The confusion of genetic material from the virus and the animal does not prove that a raccoon dog itself has been infected. And even if a raccoon dog was infected, it wouldn’t be clear whether the animal spread the virus to people. Another animal may have passed the virus to people, or someone infected with the virus may have passed the virus to a raccoon dog.
But the analysis determined that raccoon dogs — fluffy animals related to foxes and known to be capable of transmitting the coronavirus — deposited genetic signatures in the same place where the virus’s genetic material was left, the three said. scientists. That evidence, they said, was consistent with a scenario in which the virus had spread to humans from a wild animal.
A report detailing the international research team’s findings has not yet been released. Their analysis was first reported by The Atlantic.
The new evidence is sure to shake up the debate over the origins of the pandemic, even if it won’t resolve the question of how it started.
In recent weeks, the so-called lab leak theory, which posits that the coronavirus emerged from a research lab in Wuhan, has gained ground thanks to a new US Department of Energy intelligence assessment and guided hearings by the new Republican House leadership.
But genetic data from the market offers some of the most tangible evidence yet of how the virus may have leapt into people from wild animals outside of a laboratory. It also suggests that Chinese scientists have provided an incomplete account of the evidence that could provide details on how the virus was spreading in the Huanan market.
Jeremy Kamil, a virus expert at Louisiana State University’s Shreveport Center for Health Sciences who was not involved in the study, said the results showed that “samples from the market that contained early lineages of COVID were contaminated with DNA readings from wild animals”.
Kamil said there was no conclusive evidence that an infected animal had triggered the pandemic. But, he said, he “really shines a spotlight on the illegal pet trade in an intimate way.”
Chinese scientists had published a study looking at the same market samples in February 2022. That study reported that the samples tested positive for the coronavirus but suggested the virus came from infected people shopping or working in the market, rather than from animals be sold there.
At some point, those same researchers, including some affiliated with the Chinese Center for Disease Control and Prevention, sent raw swab data around the market to GISAID, an international repository of virus genetic sequences. (Attempts to reach Chinese scientists by phone on Thursday were unsuccessful.)
On March 4, Florence Débarre, an evolutionary biologist at France’s National Center for Scientific Research, was searching that database for information related to the Huanan market when, she said in an interview, she noticed more sequences popping up than usual. Confused at first that they contained new data, Débarre set them aside, only to log back in last week to find they contained a trove of raw data.
Virus experts have been waiting for raw sequence data from the market ever since they learned of its existence in a February 2022 China report. Débarre said he alerted other scientists, including the leaders of a team that had published a series of studies l ‘last year pointing to the market as the origin.
An international team, which included Michael Worobey, an evolutionary biologist at the University of Arizona; Kristian Andersen, a virus expert at the Scripps Research Institute in California; and Edward Holmes, a biologist at the University of Sydney, began mining the new genetic data last week.
One sample in particular caught their attention. It had been taken from a trolley attached to a specific Huanan market stall that Holmes visited in 2014, scientists involved in the analysis said. That barn, Holmes discovered, contained caged raccoon dogs atop a separate cage that held birds—exactly the kind of environment conducive to the transmission of new viruses.
The swab taken from a trolley there in early 2020, the research team found, contained genetic material from the virus and a raccoon dog.
“We were able to figure out relatively quickly that at least one of these samples had a lot of raccoon dog nucleic acid, along with virus nucleic acid,” said Stephen Goldstein, a virus expert at the University of Utah who worked on the new analysis (Nucleic acids are the chemical building blocks that carry genetic information.)
After the international team came across the new data, they contacted Chinese researchers who had uploaded the files with an offer to collaborate, complying with online repository rules, scientists involved in the new analysis said. Subsequently, the sequences disappeared from GISAID.
It is unclear who removed them or why they were removed.
Débarre said the research team was looking for more data, including some from market samples that have never been made public. “What’s important is that there’s even more data,” he said.
Scientists involved in the analysis said some of the samples also contained genetic material from other animals and humans. Angela Rasmussen, a virus expert at the Vaccine and Infectious Disease Organization at the University of Saskatchewan in Canada, who worked on the analysis, said human genetic material was predictable given that people shopped and worked there and that cases of COVID was linked to the market.
Goldstein also cautioned that “we don’t have an infected animal and we can’t conclusively prove that there was an infected animal in that barn.” The virus’s genetic material is stable enough, he said, that it’s not clear when exactly it was deposited on the market. He said the team was still analyzing the data and that he didn’t intend for his analysis to go public until he released a report.
“But,” he said, “since the animals that were on the market weren’t sampled at the time, this is the best we can hope to get.”
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