There is a tantalizing new clue in the hunt for the origins of the Covid-19 pandemic.
A new analysis of collected genetic material from January to March 2020 at the Huanan Seafood Market in Wuhan, China, has discovered animal DNA in samples already known to be positive for SARS-CoV-2, the coronavirus that causes Covid-19. A significant portion of that DNA appears to belong to animals known as raccoon dogs, which were known to be traded in the marketplace, according to World Health Organization officials, who covered the new evidence in a news briefing Friday.
The connection to raccoon dogs came to light after Chinese researchers shared raw genetic sequences taken from obliterated specimens collected from the market early in the pandemic. The sequences were uploaded to the data sharing site GISAID in late January 2023, but were recently removed.
An international team of researchers noticed and downloaded them for further study, WHO officials said Friday.
The new findings – which have not yet been made public – do not answer the question of how the pandemic started. They do not prove that raccoon dogs were infected with SARS-CoV-2, nor do they prove that raccoon dogs were the first animals to infect humans.
But because viruses don’t survive long in the environment outside of their hosts, it’s highly suggestive that so much of the virus’s genetic material was mixed with genetic material from raccoon dogs that they may have been carriers, according to scientists who worked on the analysis. The analysis was conducted by Kristian Andersen, an immunologist and microbiologist at Scripps Research; Edward Holmes, a virologist at the University of Sydney; Michael Worobey, an evolutionary biologist at the University of Arizona. These three scientists, who have delved into the origins of the pandemic, were interviewed by reporters from The Atlantic magazine. CNN has contacted Andersen, Holmes and Worobey for comment.
The data of the international analysis was first reported by The Atlantic on Thursday.
The new data comes as Republicans in Congress have opened an investigation into the origins of the pandemic. Previous studies provided evidence that the virus likely entered the market naturally, but could not point to a specific origin. Some US agencies, including a recent assessment by the US Department of Energy, say the pandemic is likely the result of a lab leak in Wuhan.
In Friday’s press conference, WHO Director-General Tedros Adhanom Ghebreyesus said the organization had first been informed of the sequences on Sunday.
“As soon as we became aware of this data, we contacted the Chinese CDC and urged them to share it with WHO and the international scientific community so that it can be analyzed,” Tedros said.
The WHO also convened its Scientific Advisory Group on the Origin of the Emerging Pathogens, known as SAGO, which has been exploring the roots of the pandemic, to discuss the data on Tuesday. The group heard from Chinese scientists who originally studied the sequences, as well as from the group of international scientists who reviewed them.
WHO experts said in Friday’s briefing that the data is not conclusive. They still can’t say if the virus leaked from a lab, or if it passed naturally from animals to humans.
“These data don’t provide a definitive answer to how the pandemic started, but every piece of data is important in getting us closer to that answer,” Tedros said.
What the sequences do prove, WHO officials said, is that China has more data possibly linked to the origins of the pandemic that it has not yet shared with the rest of the world.
“This data could and should have been shared three years ago,” Tedros said. “We continue to call on China to be transparent in data sharing and to conduct necessary investigations and share results.
“Understanding how the pandemic started remains a moral and scientific imperative.”
CNN contacted the Chinese scientists who first analyzed and shared the data, but received no response.
The Chinese researchers, who are affiliated with that country’s Center for Disease Control and Prevention, had shared their own analysis of the 2022 samples. In that preprint study published last year, they concluded that “no animal host of SARS-CoV2 can be derived.”
The study looked at 923 environmental samples from the fish market and 457 samples from animals, and found 63 environmental samples positive for the virus that causes Covid-19. Most are from the western end of the market. None of the animal samples taken from refrigerated and frozen products on sale and from live, stray animals roaming the market were positive, the Chinese authors wrote in 2022.
When they looked at the different types of DNA represented in the environmental samples, the Chinese authors saw a link only to humans, but not to other animals.
Then recently an international team of researchers Taking a new look at the genetic material in the samples — which were swabbed in and around the market stalls — using an advanced genetic technique called metagenomics, scientists said they were surprised to find a significant amount of DNA that belonged to raccoon dogs, a small animal related to foxes. Raccoon dogs can be infected with the virus that causes Covid-19 and are high on the list of suspected animal hosts for the virus.
“What they found is molecular evidence that animals were sold in that market. That was suspected, but they found molecular evidence for it. And also that some of the animals that were there were susceptible to SARS-CoV2 infection, and some of those animals were raccoon dogs,” Maria Van Kerkhove, WHO’s technical lead for Covid-19, said at Friday’s briefing.
“This does not change our approach to studying the origins of Covid-19. It just tells us that there is more data and that data needs to be fully shared,” she said.
Van Kerkhove said that until the international scientific community can assess more evidence, “all hypotheses remain on the table”.
Some experts found the new evidence convincing, if not completely convincing, of a market origin.
“The data points even further to a market origin,” said Andersen, the Scripps Research evolutionary biologist who attended the WHO. meeting and is one of the scientists analyzing the new data, told Science magazine.
The claims about the new data quickly sparked debate in the scientific community.
Francois Balloux, director of the Genetics Institute at University College London, said the fact that the new analysis had not yet been posted publicly for scientists to examine, but had come to light in news reports, warranted caution.
“Articles like that really don’t help, they just further polarize the debate,” Balloux wrote in a thread Twitter. “Those convinced by a zoonotic origin will read it as the definitive evidence for their conviction, and those convinced it was a lab leak will interpret the weakness of the evidence as attempts at cover-up.”
Other experts, not involved in the analysis, said the data could hold the key to showing that the virus has a natural origin.
Felicia Goodrum is an immunobiologist at the University of Arizona who recently published a review of all available data for the various theories behind the origin of the pandemic.
Goodrum says the strongest evidence for a natural spillover would be to isolate the virus that causes Covid-19 from an animal that was on the market in 2019.
“Obviously that’s impossible, as we can’t go back in time any more than we did through sequencing, and no animals were present at the time for sequences to be collected. For me, this is the one second best,” Goodrum said in an email to CNN.
In the WHO briefing, Van Kerkhove said the Chinese CDC researchers uploaded the sequences to GISAID as they were updating their original study. She said their first paper is currently being updated and resubmitted for publication.
“GISAID has told us that China’s CDC data is being updated and expanded,” she said.
Van Kerkhove said on Friday that what the WHO would like to do is to find the source where the animals came from. Were they wild? Were they farmed?
she said in the course of her investigation into the origins of the pandemic, WHO China had repeatedly asked for studies to trace the animals back to their source farms. She said the WHO had also asked for blood tests on people working in the market, as well as tests on animals that may have come from the farms.
“Share the data,” said Dr. Mike Ryan, executive director of WHO’s health emergencies program, Friday, addressing scientists around the world who may have relevant information. “Let science do the work and we’ll get the answers.”