Genetic material collected at a Chinese market near where the first human cases of COVID-19 were identified shows raccoon dog DNA mixed with the virus, adding evidence to the theory that the virus originated in animals, not a human. laboratory, say international experts.
“These data do not provide a definitive answer as to how the pandemic started, but each piece of data is important in getting us closer to that answer,” World Health Organization Director-General Tedros Adhanom Ghebreyesus said Friday.
How the coronavirus emerged remains unclear. Many scientists believe it most likely jumped from animals to people, as many other viruses have in the past, at a wildlife market in Wuhan, China. But Wuhan is home to several laboratories involved in collecting and studying coronaviruses, fueling theories that scientists say are plausible that the virus leaked from one.
The new findings do not settle the question and have not been formally reviewed by other experts or published in a peer-reviewed journal.
Tedros criticized China for not sharing genetic information sooner, telling a news conference that “this information could and should have been shared three years ago.”
Samples were collected from surfaces at the Huanan Seafood Market in early 2020 in Wuhan, where the first human cases of COVID-19 were found in late 2019.
Tedros said scientists from the Chinese Center for Disease Control and Prevention recently uploaded the genetic sequences to the world’s largest public virus database.
They were then removed, but not before a French biologist discovered the information by chance and shared it with a group of scientists outside of China investigating the origins of the coronavirus.
The data shows that some of the COVID-positive samples collected from a post known to be involved in the wildlife trade also contained raccoon dog genes, indicating that the animals may have been infected with the virus, according to the researchers. scientists. Their analysis was first reported in The Atlantic.
“There’s a good chance that the animals that deposited that DNA also deposited the virus,” said Stephen Goldstein, a virologist at the University of Utah who participated in the data analysis. “If you were to go and do environmental sampling after a zoonotic spill event… this is basically exactly what you would expect to find.”
The canines, named for their raccoon-like faces, are often farmed for their fur and sold for meat in animal markets across China.
Ray Yip, an epidemiologist and founding member of the US Centers for Disease Control office in China, said the findings are significant, though not conclusive.
“The market environmental sampling data released by the China CDC is by far the strongest evidence to support animal origins,” Yip told the AP in an email. He was not connected to the new analysis.
WHO’s COVID-19 technical lead Maria Van Kerkhove cautioned that the analysis did not find the virus inside any animals, nor did it find any strong evidence that any animals infected humans.
“What this provides are clues to help us understand what might have happened,” he said. The international group also told the WHO that they found DNA from other animals, as well as raccoon dogs, in samples from the seafood market, he added.
The genetic code of the coronavirus is strikingly similar to that of bat coronaviruses, and many scientists suspect that COVID-19 jumped to humans directly from a bat or through an animal intermediary such as pangolins, ferrets, or raccoon dogs.
Efforts to determine the origins of the COVID-19 pandemic have been complicated by factors including the massive increase in human infections in the first two years of the pandemic and an increasingly bitter political dispute.
It took virus experts more than a dozen years to identify the animal origin of SARS, a related virus.
Goldstein and his colleagues say their analysis is the first strong indication that coronavirus-infected wild animals may be on the market. But it’s also possible that humans brought the virus to market and infected the raccoon dogs, or that infected humans simply left traces of the virus near the animals.
After the group’s scientists contacted the Chinese CDC, they say, the sequences were removed from the global virus database. The researchers are puzzled as to why data from samples collected more than three years ago were not made public sooner. Tedros has pleaded with China to share more of its COVID-19 research data.
Gao Fu, the former head of the Chinese CDC and lead author of the Chinese article, did not immediately respond to an Associated Press email requesting comment. But he told Science magazine that the sequences “are nothing new. It was known that there was illegal trafficking of animals and that is why the market was closed immediately.
Goldstein said his group presented their findings this week to a WHO advisory panel investigating the origins of COVID-19.
Michael Imperiale of the University of Michigan, an expert in microbiology and immunology who was not involved in the data analysis, said that finding a sample with sequences from the virus and a raccoon dog “puts the virus and the dog very close. But he doesn’t necessarily say the dog was infected with the virus; he just says they were in the same very small area.”
He said most of the scientific evidence at this point supports a natural exposure in the market, pointing to research published last summer showing the market was likely the early epicenter of the scourge and concluding that the virus spread from animals. people on two separate occasions. . “What is the chance that there are two different lab leaks?” she asked.
Mark Woolhouse, an infectious disease expert at the University of Edinburgh, said it will be crucial to see how the genetic sequences of raccoon dogs match up with what is known about the historical evolution of the COVID-19 virus. If dogs are shown to have COVID and those viruses are shown to have earlier origins than those that infected people, “that’s probably the best evidence we can hope for that this was a spillover event in the marketplace.”
After a week-long visit to China to study the origins of the pandemic, the WHO released a report in 2021 concluding that COVID-19 most likely jumped from animals to humans, ruling out the possibility of a single origin. laboratory as “extremely unlikely”.
But the UN health agency backtracked the following year, saying “key data” was still missing. And Tedros has said that all hypotheses remain on the table.
Scientists at the China CDC who previously analyzed the samples from the Huanan market published a paper as a preprint in February that suggested that humans brought the virus to the market, not animals, implying that the virus originated elsewhere. His article did not mention that animal genes were found in the samples that tested positive.
In February, the Wall Street Journal reported that the US Department of Energy had assessed “with little confidence” that the virus had leaked from a laboratory. But others in the US intelligence community disagree, believing it more likely first came from animals.
Experts say the true origin of the pandemic may not be known for many years, if ever.