Beijing: Raccoon dog DNA has been found in genetic samples taken from a Chinese market close to the site of the first cases of COVID-19 in humans, adding support to the idea that the virus originated from animals rather than a lab, according to international experts.
"These data do not provide a definitive answer to how the pandemic began, but every piece of data is important to moving us closer to that answer," World Health Organization Director-General Tedros Adhanom Ghebreyesus said Friday.
Uncertainty surrounds the coronavirus's emergence. Like numerous other viruses before it, many scientists think it most likely spread from animals to humans at a wildlife market in Wuhan, China. However, Wuhan is home to several laboratories that collect and study coronaviruses, supporting theories that the virus may have leaked from one, according to experts.
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The new findings do not settle the question, and they have not been formally reviewed by other experts or published in a peer-reviewed journal. At a press conference, Tedros blasted China for not disclosing the genetic data sooner, claiming that "this data could have and should have been shared three years ago."
In Wuhan, where the first human cases of COVID-19 were discovered in late 2019, the samples were taken from surfaces at the Huanan seafood market in early 2020.
Tedros claimed that researchers at the Chinese Center for Disease Control and Prevention recently uploaded the genetic sequences to the largest public virus database in the world.
They were later taken down, but not before a French biologist accidentally discovered the data and informed a team of researchers outside of China who are examining the coronavirus's ancestry.
According to the data, some of the COVID-positive samples gathered from a stall suspected of dealing in wildlife trade also contained raccoon dog genes, suggesting the animals may have been exposed to the virus. The Atlantic published a first account of their analysis.
Stephen Goldstein, a virologist at the University of Utah who worked on the data analysis, said that there is a good chance that the animals that deposited that DNA also deposited the virus. "This is basically exactly what you would expect to find if you were to go and do environmental sampling in the aftermath of a zoonotic spillover event."
The dogs, which got their name because of their raccoon-like faces, are frequently bred for their fur and offered for sale as meat in animal markets all over China. Even though the results aren't conclusive, epidemiologist Ray Yip, a founding member of the US Centers for Disease Control office in China, said the findings are significant.
The strongest evidence in favour of animal origins, according to Yip, is the market environmental sampling data published by China's CDC, he wrote in an email to the AP. He was not connected to the new analysis.
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Maria Van Kerkhove, the technical lead for COVID-19 at WHO, issued a warning that neither the analysis nor any hard data indicated that any animals had infected humans.
She said, "What this does is give us hints to help us understand what might have happened. She continued, "The international group also reported to WHO that the samples from the seafood market contained DNA from other animals in addition to raccoon dogs.
Given the striking genetic similarity between the coronavirus and bat coronaviruses, many researchers believe COVID-19 entered humans either directly from a bat or via an intermediary animal like a pangolin, ferret, or racoon dog.
The massive increase in human infections during the COVID-19 pandemic's first two years as well as an increasingly acrimonious political dispute have complicated efforts to pinpoint the cause of the outbreak.
A related virus called SARS was traced back to an animal more than a dozen years ago by virus experts.
According to Goldstein and his associates, their analysis is the first conclusive proof that there might have been coronavirus-infected wildlife at the market. However, it's also possible that people brought the virus to the market and infected the raccoon dogs, or that sick people accidentally dropped virus remnants close to the animals.
The sequences, according to the group's scientists, were taken out of the global virus database after they got in touch with the China CDC. Why information on samples taken more than three years ago wasn't made public earlier is a mystery to researchers. China has been urged by Tedros to divulge more of its COVID-19 research data.
An email from the Associated Press seeking comment to Gao Fu, the former head of the Chinese CDC and lead author of the Chinese paper, was not immediately returned. The sequences, however, he claimed to Science magazine, "are nothing new. The market was immediately closed because it was known that there was illegal animal dealing.
According to Goldstein, his team's findings were presented this week to a WHO advisory panel looking into the origins of COVID-19.
Microbiology and immunology specialist Michael Imperiale of the University of Michigan said the discovery of a sample containing the virus' and a raccoon dog's sequences "places the virus and the dog in very close proximity." Imperiale was not involved in the data analysis. However, it only indicates that they were in the same extremely condensed area, not that the dog was infected with the virus.
He cited research from last summer that suggested the market was probably the early epicentre of the calamity and came to the conclusion that the virus spread from animals into people twice. He claimed that the majority of the scientific evidence at this point supports a natural exposure at the market. He enquired as to the likelihood of there being two distinct lab leaks.
It will be crucial to compare the genetic sequences of the raccoon dogs to what is known about the past evolution of the COVID-19 virus, according to Mark Woolhouse, an infectious diseases specialist at the University of Edinburgh. It's probably the best proof we can hope for that this was a market spillover event if the dogs are found to have COVID and those viruses turn out to have earlier origins than the ones that infected people.
After spending several weeks in China researching the origins of the pandemic, WHO published a report in 2021 stating that COVID-19 most likely entered humans from animals and labelling the likelihood of a lab origin as "extremely unlikely."
The UN health organisation later apologised, claiming that "key pieces of data" were still missing. Tedros has also stated that all theories are still valid.
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In a paper published as a preprint in February, the China CDC researchers who had previously examined the samples from the Huanan market suggested that humans, not animals, had brought the virus to the market, indicating that the virus originated elsewhere. The fact that animal genes were discovered in the samples that tested positive is not mentioned in their paper.
The US Department of Energy determined "with low confidence" that the virus had leaked from a lab, according to a Wall Street Journal report from February. Others in the US intelligence community, however, disagree and think it was probably first created by animals. According to experts, it may be many years, if ever, before the true cause of the pandemic is discovered.