China publishes data showing the DNA of raccoon dogs in a Wuhan market

Chinese government scientists on Wednesday published a long-awaited study of a market in the city of Wuhan, acknowledging that animals exposed to the coronavirus were present around the time the virus emerged. But scientists also said it is still not clear how the epidemic began.

the study, Published in the journal Nature, focus on swabs taken from surfaces in early 2020 at the Huanan Seafood Wholesale Market, a large market where many of the first known Covid patients worked or shopped. Chinese scholars have published a dossier An early version of their genetic analysis of those samples in February 2022, but at that time it downplayed the potential for infection in the animals on the market.

The scientists, many of whom are affiliated with the Chinese Center for Disease Control and Prevention, also wanted to publish their data in a peer-reviewed journal. As part of this process, the scientists uploaded more genetic sequence data to a large international database, and Database officials said last month.

A few weeks after the data was released, a team of international scientists who had been studying the origins of the pandemic said they had found the sequence. They found that the samples that tested positive for the coronavirus contained genetic material belonging to the animals, including large amounts that were identical to a raccoon dog, a fluffy mammal sold for its fur and meat known to be able to spread the coronavirus.

This analysis is the subject of a The report was published online in late MarchIt has not been proven that the raccoon dog itself was infected or that the animals gave the virus to people. But it proved that raccoon dogs deposited their genetic fingerprints in the same place where they left the genetic material from the virus.

Several virologists said that this scenario corresponds to a scenario in which the virus spread to people from a wild animal that was illegally traded in the market.

The international team’s analysis appears to have precipitated the release of the Chinese scientists’ study on the same data: The article appeared Wednesday on Nature’s website with a note saying it had been accepted for publication, but it was still an “early version” and not yet edited.

Several CDC-affiliated authors of the article, William J. Liu, George Gao, and Guizhen Wu, did not respond to requests for comment.

In their first version of the article from February 2022, the Chinese authors did not mention finding any genetic material from raccoon dogs in market swabs, which were taken from walls, floors, metal cages, and carts. Furthermore, they said the data did not refer to any infected animals.

But in Wednesday’s issue just over a year later, they wrote that the study “confirmed the presence of raccoon dogs” and other animals at risk of contracting the coronavirus on the market.

Many scientists believe that current evidence indicates that those animals likely acted as intermediate hosts for the virus, which may have originated in bats. But they also say the evidence does not completely rule out a scenario in which people gave the virus to animals at the market.

The Chinese authors emphasized that uncertainty in the new study. They also raised the idea that the virus could have been brought to the Wuhan market on packages of frozen foods, also known as cold chain products. Many scientists consider this scenario very unlikely, but China has promoted it because it gives credence to the idea that the epidemic could have started outside the country and arrived via imported foods.

“The possibility of the virus entering the market through infected humans, or cold chain products, cannot be ruled out,” the article said.

Outside scientists said in interviews on Wednesday that the study had several other improbable findings as well. For example, he said, the swabs contain genetic material from a number of animals that are almost certainly not on the market, including pandas, chimpanzees and mole rats.

Alice Hughes, an associate professor at the University of Hong Kong who focused on conservation biology, said the inclusion of those animals indicated either that the authors had incorrectly classified the genetic material or that the samples were contaminated during in vitro sequencing.

“The greatest asset of this paper is the fact that it releases a data set for other scientists to analyze more carefully and responsibly,” said Dr Hughes. “Because of the glaring errors in this analysis, the analysis was not performed in a manner rigorous enough to have confidence in any of the results.”

Asked how Nature’s peer-review process handled the species findings, a spokesperson for the journal noted that the authors included a warning that the list of identified species on the market was “not definitive” and that further analysis was needed.

For the international scientists who first reported detecting signs of raccoon dogs in Covid-positive swabs last month, Nature’s latest study left a number of important questions unanswered about the methods the Chinese team used to analyze the sequence.

Still, the post, as well as an earlier version of it published online They provided important new data, including the number of swabs taken from each stall in the market, Alexandre Kretz-Kristof, a former Johns Hopkins University postdoctoral researcher and computational biologist who helped lead the international team’s analysis, said last week. .

With this information, Dr. Kretz-Christophe said he and his collaborators were able to confirm an important finding: Swabs taken from the corner of a market selling wild animals were more likely to test positive for the virus, a result that could only be explained by the Chinese researchers after taking more Samples from that angle, he said.

“It’s a very impressive dataset and the relevance is very high,” said Dr. Kritz-Christophe of the market sampling. Because of that, I think it’s a good idea to publish this data in the scientific record, even if I don’t agree with every explanation. “