An international team of virus experts said on Thursday they had found genetic data from a market in Wuhan, China, linking the coronavirus to raccoon dogs for sale there, adding evidence to the case that the worst pandemic in a century could have been caused by an infected animal being treated through the illegal wildlife trade.
The genetic data was extracted from swabs taken in and around the Huanan Seafood Wholesale Market beginning in January 2020, shortly after the market was closed by Chinese authorities due to suspicions that it was linked to the outbreak of a new virus. . By then, the animals had been removed, but the researchers cleaned walls, floors, metal cages and carts often used to transport animal cages.
In samples that tested positive for the coronavirus, the international research team found genetic material belonging to animals, including large amounts that matched raccoon dogs, three scientists involved in the analysis said.
The mixing of genetic material from the virus and from the animal does not prove that a raccoon dog itself was infected. And even if a raccoon dog had been infected, it would not be clear that the animal transmitted the virus to people. Another animal could have passed the virus to people, or someone infected with the virus could have passed it to a raccoon dog.
But the analysis established that raccoon dogs, furry animals that are related to foxes and are known to transmit the coronavirus, deposited genetic signatures in the same place where the virus’s genetic material was left, the three scientists said. That evidence, they said, was consistent with a scenario in which the virus had spread to humans from a wild animal.
A report containing the full details of the international investigation team’s findings has yet to be published. His analysis was first reported by the atlantic.
The new evidence is sure to upend the debate about the origins of the pandemic, even if it doesn’t settle the question of how it started.
In recent weeks, the so-called laboratory leak theory, which postulates that the coronavirus emerged from a research laboratory in Wuhan, has gained traction thanks to a new intelligence test from the US Department of Energy and hearings led by the new House Republican leadership.
But genetic data on the market offers some of the most tangible evidence yet of how the virus could have spread to people from wild animals outside of a laboratory. It also suggests that Chinese scientists have given an incomplete account of evidence that could fill in the details about how the virus was spreading in the Huanan market.
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Jeremy Kamil, a virologist at the Louisiana State University Shreveport Health Sciences Center who was not involved in the study, said the findings showed that “market samples that had early Covid lineages were contaminated with DNA reads from wild animals”.
Dr. Kamil said that was not conclusive evidence that an infected animal had triggered the pandemic. But, he said, “it really highlights the illegal trade in animals in an intimate way.”
Chinese scientists had launched a study looking at the same samples from the market in February 2022. That study reported that the samples tested positive for the coronavirus, but suggested that the virus came from infected people who were shopping or working at the market, rather than from animals being sold there.
At some point, those same researchers, including some affiliated with the Chinese Center for Disease Control and Prevention, published the raw data from the market swabs on GISAID, an international repository of virus genetic sequences. (Attempts to reach the 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 appearing than usual. Confused at first about whether they contained new data, Dr. Débarre put them aside, only to log in again last week to discover that they contained a large amount of raw data.
Virus experts had been waiting for such raw sequence data from the market since learning of its existence in the February 2022 Chinese report. Dr. Débarre said she had alerted other scientists, including the leaders of a team that had published a set of studies last year pointing to the market as the source.
An international team, including Michael Worobey, an evolutionary biologist at the University of Arizona; Kristian Andersen, a virologist 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 his eye. It had been taken from a cart linked to a specific stall in the Huanan market that Dr. Holmes had visited in 2014said the scientists involved in the analysis. That stall, Dr. Holmes discovered, contained caged raccoon dogs on top of a separate cage with birds—exactly the kind of environment conducive to the transmission of new viruses.
The swab taken from a car 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 in at least one of these samples there was a lot of raccoon dog nucleic acid, along with nucleic acid from the virus,” said Stephen Goldstein, a virologist at the University of Utah who worked on the study. new analysis. (Nucleic acids are the basic chemical building blocks that carry genetic information.)
After the international team stumbled upon the new data, it approached the Chinese researchers who had uploaded the files with an offer to collaborate, following the rules of online repository, the scientists involved in the new analysis said. After that, the sequences disappeared from GISAID.
It is unclear who removed them or why they were removed.
Dr. Débarre said the research team was looking for more data, including some from market samples that were never made public. “The important thing is that there is still more data,” he said.
The scientists involved in the analysis said that some of the samples also contained genetic material from other animals and humans. Angela Rasmussen, a virologist with the Organization for Vaccines and Infectious Diseases at the University of Saskatchewan in Canada, who worked on the analysis, said the human genetic material was to be expected given that people were shopping and working there and that human cases of covid had been linked to the market.
Dr. Goldstein also cautioned that “we do not have an infected animal and we cannot definitively prove that there was an infected animal at that stall.” The virus’s genetic material is stable enough, he said, so it’s not clear when exactly it was deposited on the market. He said the team was still analyzing the data and did not intend to make its analysis public before publishing a report.
“But,” he said, “since the animals that were present at the market were not sampled at the time, this is the best we can hope to get.”