International scientists who examined previously unavailable genetic data from samples collected at a market near where the first human cases of COVID-19 were detected in China said they found evidence that the pandemic originated in animals, not a laboratory.
Other experts have yet to verify their analysis, which also has not yet appeared in a peer-reviewed journal. How the coronavirus first began to make people sick remains uncertain.
“These data do not provide a definitive answer to how the pandemic started, but every piece of evidence is important in bringing us closer to that answer,” WHO Director-General Tedros Adhanom Ghebreyesus said at a press conference on Friday.
He also criticized China for not sharing the genetic information earlier, adding that “this data could and should have been shared three years ago.”
The samples were collected from surfaces in the Huanan Seafood Market in Wuhan after the first human cases of COVID-19 were found in late 2019.
Tedros said the genetic sequences were uploaded to the world’s largest public database of viruses in late January by scientists at the Chinese Center for Disease Control and Prevention. the data has been removed from the database.
A French biologist found the information by chance while trawling through the database and shared it with a group of scientists based outside of China looking into the origins of the coronavirus.
Genetic sequencing data showed that some of the samples, which were known to be positive for the coronavirus, also contained genetic material from raccoon dogs, indicating that the animals may have been infected with the virus, the scientists said. Their analysis was first reported in The Atlantic.
“There’s a good chance that the animals that deposited this DNA also deposited the virus,” said Stephen Goldstein, a virologist at the University of Utah who was involved 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.”
Ray Yip, an epidemiologist and founding member of the US Centers for Disease Control’s China office, said that while the new findings were not definitive, they were important.
“The market environmental sampling data published by the China CDC is by far the strongest evidence in support of an animal origin,” Yip told the AP in an email. It was not linked to the new analysis.
Scientists have been searching for the origins of the COVID-19 pandemic since the virus first appeared, but that search has been complicated by factors such as a massive increase in human infections in the first two years of the pandemic and an increasingly bitter political dispute.
It took virologists more than a dozen years to identify the animal origin of SARS, a related virus.
The researchers say their analysis is the first solid indication that there may have been wildlife infected with the coronavirus on the market. Some of the samples with raccoon dog DNA were collected from a stall that tested positive for COVID-19 and was known to be involved in the wildlife trade, Goldstein said.
But it’s also possible that humans brought the virus to market first and infected the raccoon dogs, or that infected humans happened to leave traces of the virus near the animals.
After the team’s scientists contacted China’s CDC, they say, the sequences were retrieved from the global virus database. The researchers are questioning why the data on the samples collected three years ago were not made public earlier.
Earlier this week, some of the scientists presented their findings to an advisory group tasked by the World Health Organization to investigate the origins of COVID, Goldstein confirmed.
Mark Woolhouse, an infectious disease expert at the University of Edinburgh, said it will be important to see how the genetic sequences from the raccoon dogs fit with what is known about the historical evolution of the COVID-19 virus.
He said that if the analysis shows that the animal viruses predate those that infected humans, “that’s probably as good evidence as we can expect to get that this was a secondary event in the marketplace.”
After a week-long visit to China to study the origins of the pandemic, the WHO published a report in 2021 concluding that COVID likely jumped to humans from animals, dismissing the possibility of a laboratory origin as “extremely unlikely”.
But the UN health agency backtracked the following year, saying “key pieces of data” were still missing.
In recent months, WHO director Tedros said all cases remained on the table, while he and senior officials pleaded with China to share more data on their research into COVID-19.
China’s CDC scientists who previously analyzed the samples published a paper as a preprint in February. Their analysis showed that humans brought the virus to market, not animals, implying that the virus came from elsewhere.
The paper did not report that animal genetic material was found in samples that tested positive for COVID-19, and the authors did not upload the raw data until March. Gao Fu, the former head of China’s CDC and lead author of the paper, did not immediately respond to an email seeking comment.
Wuhan, the Chinese city where COVID-19 was first identified, is home to several laboratories dedicated to collecting and studying coronaviruses, fueling theories that the virus may have leaked from one.
In February, the Wall Street Journal reported that the US Department of Energy had assessed “with low confidence” that the virus had leaked from a laboratory. But others in the US intelligence community disagree, believing it more likely to have come from animals in the first place. Experts say the true origins of the pandemic may not be known for many years – if ever.