Newly released genetic data collected from a live food market in Wuhan has linked Covid-19 to raccoon dogs, giving weight to the theory that infected animals sold at the site started the coronavirus pandemic, say at work involved researchers.
Swabs collected from stalls at the Huanan Seafood Market in the two months following the January 1, 2020 closure, were previously found to contain both Covid and human DNA. When the results were released last year, Chinese researchers said the samples did not contain any animal DNA.
This conclusion has now been refuted by an international team of scientists. Their analysis of gene sequences published by the Chinese team in the scientific database Gisaid found that some of the Covid-positive samples were rich in raccoon dog DNA. Trace amounts of DNA from other mammals, including civet cats, were also present in Covid-positive samples.
The discovery does not prove that raccoon dogs or other animals infected with Covid caused the pandemic, but scientists who presented the work to a World Health Organization expert panel on Tuesday believe it is more likely.
“The data further point to a market origin,” Prof. Kristian Andersen, an evolutionary biologist at Scripps Research in La Jolla, Calif., told Science magazine. Andersen attended a meeting of the WHO Scientific Advisory Group on the Origins of Novel Pathogens and is working on the data.
The recently uploaded gene sequences were discovered by Florence Débarre, an evolutionary biologist at the French National Center for Scientific Research. She alerted Andersen and Prof. Michael Worobey, an evolutionary biologist at the University of Arizona, who both have written papers providing evidence of a market origin for the pandemic.
What sparked the worst pandemic in a century has become the focus of intense — and often venomous — debate. One theory is that the virus emerged in wild animals and spread to humans through contamination at the market. Another suspects it escaped from the nearby Wuhan Institute of Virology, where researchers are working on similar pathogens.
The lab leak theory has made headlines in recent weeks following an intelligence assessment by the US Department of Energy and Republican-led hearings into the origins of the pandemic. Concrete evidence for both theories is lacking and may never be found.
The latest genetic data does not show that raccoon dogs or other mammals were infected with Covid and spread it in the market. If the animals were infected, they may have contracted the virus from infected humans. However, the results point to the possibility that the cause was an infected animal and ultimately the illegal wildlife trade.
While scientists expect the debate to continue, there are questions as to why the Chinese team didn’t release the genetic data sooner. A member of the team, George Gao, the former head of the China Centers for Disease Control and Prevention, told Science that the sequences contained “nothing new.” Why the data was later pulled from the Gisaid site is also not clear.
Débarre said she was preparing a report of the findings to be published and would not answer questions until that was done.
dr Jonathan Stoye, virologist and senior group leader at the Francis Crick Institute in London, said: “The finding of Sars-CoV-2 infected raccoon dogs reinforces the plausibility that farm animals infected with coronavirus were an important link in the chain of events leading to the Covid-19 outbreak. 19 pandemic led.
“However, it does not disprove lab leak theories: that would require proof that such animals were infected prior to their arrival and display at the Huanan fish market, which may never be possible.”
Also on Friday, the WHO said the Covid-19 pandemic may calm down this year, posing a flu-like threat.
“I think we’re getting to a point where we can look at Covid-19 the same way we look at seasonal influenza: a health threat, a virus that will continue to kill, but a virus that isn’t disrupting our society,” he said Michael Ryan, WHO’s Director of Emergencies, added: “I believe that’s coming… this year.”