(CNN) — There is a tantalizing new lead in the search for the origins of the covid-19 pandemic.
A new analysis of genetic material collected 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 the covid-19. A significant amount 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 discussed the new evidence at a news briefing on Friday.
The raccoon dog connection came to light after Chinese researchers shared raw genetic sequences taken from samples picked up on the market early in the pandemic. The sequences were uploaded in late January 2023 to the GISAID data sharing site, but have recently been removed.
An international team of researchers noticed them and downloaded them for further study, WHO officials said Friday.
The new findings, which have not yet been published, do not settle 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 people.
But because viruses don’t survive in the environment outside their hosts for very long, finding so much genetic material from the virus interspersed with genetic material from raccoon dogs suggests they might have been carriers, according to the scientists who worked on the analysis.
The analysis was led 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 been investigating the origins of the pandemic, were interviewed by reporters from The Atlantic magazine. CNN has reached out to Andersen, Holmes and Worobey for comment.
The details of the international analysis were reported for the first time this Thursday by The Atlantic.
The new data is emerging as Republicans in Congress have opened investigations into the origin of the pandemic. Previous studies provided evidence that the virus likely arose naturally on the market, but were unable to pinpoint a specific origin.
Some US agencies, including a recent assessment by the US Department of Energy, say the pandemic likely stemmed from a laboratory leak in Wuhan.
What the samples show
At a press conference on Friday, WHO Director-General Tedros Adhanom Ghebreyesus said the organization first learned of the footage on Sunday.
“As soon as we learned of this data, we contacted the Chinese CDC and urged them to share it with the WHO and the international scientific community so that it can be analyzed,” Tedros said.
The WHO also convened its Scientific Advisory Group on the Origins of Novel Pathogens, known as SAGO, which has been investigating the roots of the pandemic, to discuss the data on Tuesday. The group heard from the Chinese scientists who had originally studied the sequences, as well as from the group of international scientists who reexamined them.
WHO experts told a briefing on Friday that the data is inconclusive. They still can’t say if the virus leaked from a laboratory or was transmitted naturally from animals to humans.
“These data do not provide a definitive answer to the question of how the pandemic started, but each piece of data is important in getting us closer to that answer,” Tedros said.
What the footage does prove, WHO officials said, is that China has more data that could be 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 sharing data and to carry out the necessary investigations and share the results.
“Understanding how the pandemic began remains a moral and scientific imperative.”
CNN has reached out to the Chinese scientists who first analyzed and shared the data, but has not heard back.
There is more data out there
The Chinese researchers, who are affiliated with the Chinese Centers for Disease Control and Prevention, shared their own analysis of the samples in 2022. In that preliminary study published last year, they concluded that “no animal host can be inferred of SARS-CoV2”.
The investigation analyzed 923 environmental samples taken inside the seafood market and 457 samples taken from animals, and found 63 environmental samples that tested positive for the virus that causes covid-19. Most were taken from the western end of the market. None of the animal samples, which were taken from chilled and frozen products for sale, and from live stray animals roaming the market, were positive, the Chinese authors wrote in 2022.
When they looked at the different DNA species represented in the environmental samples, the Chinese authors only saw a link to humans, but not to other animals.
When an international team of researchers recently analyzed the genetic material in the samples, which were swabbed in and around market stalls, using an advanced genetic technique called metagenomics, the scientists said they were surprised to find a significant amount of DNA belonging to to raccoon dogs, a small animal related to foxes.
Raccoon dogs can be infected with the virus that causes covid-19 and have been 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 of that. And also that some of the animals that were there were susceptible to SARS-CoV2 infection, and some of those animals include raccoon dogs,” Maria Van Kerkhove, WHO technical lead for covid-19, said at the briefing. of this Friday.
“This does not change our approach to study the origins of covid-19. It just tells us that more data exists and that data needs to be shared in its entirety,” he said.
Van Kerkhove said that until the international scientific community can review more evidence, “all hypotheses remain on the table.”
More evidence of a natural origin?
Some experts found the new evidence persuasive, if not entirely convincing, of a market origin.
“The data further points to a market origin,” 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 made about the new data quickly sparked debate in the scientific community.
Francois Balloux, director of the Institute of Genetics at University College London, said the fact that the new analysis has not yet been released publicly for scientists to analyze, but has surfaced in news reports, warrants caution. .
“Such articles don’t really help as they only further polarize the debate,” Balloux posted in a thread on Twitter. “Those convinced of a zoonotic origin will read it as final proof of their conviction, and those convinced it was a laboratory leak will interpret the weakness of the evidence as cover-up attempts.”
Other experts, who were not involved in the analysis, said the data could be key to proving that the virus has a natural origin.
Felicia Goodrum is an immunobiologist at the University of Arizona who recently published a review of all the available data for the various theories behind the origin of the pandemic.
Goodrum says that the strongest proof of a natural contagion would be isolating the virus that causes covid-19 from an animal that was present at the market in 2019.
“Clearly, that’s impossible, as we can’t go back in time any further than we have through sequencing, and no animals were present at the time the sequences could be collected. For me, this is the next best thing,” Goodrum said in an email to CNN.
At the WHO briefing, Van Kerkhove said Chinese researchers at the CDC had uploaded the sequences to GISAID while updating their original research. He said that the first article of his is in the process of being updated and resubmitted for publication.
“GISAID has told us that the China CDC data is being updated and expanded,” he said.
Van Kerkhove said Friday that what the WHO would like to be able to do is find the source where the animals came from. Were they wild? Were they cultivated?
She said that in the course of its investigation into the origins of the pandemic, the WHO had repeatedly asked China for studies to trace the animals back to their farms of origin. She said the WHO had also asked for blood tests from people working in the market, as well as tests on animals that might have come from farms.
“Share the data,” Dr. Mike Ryan, executive director of WHO’s health emergencies program, said Friday, addressing scientists around the world who might have relevant information. “Let science do the work and we’ll get the answers.”