WHO accuses China of withholding data on Covid origins

“Scientifically, this doesn’t prove that raccoon dogs were the source, but it definitely smells like infected raccoon dogs were in the market,” said Jeremy Kamil, a virologist at Louisiana State University Health Sciences Center Shreveport.

He added, “It raises more questions about what the Chinese government really knows.”

Scientists have warned that it is unclear whether genetic material from the virus and raccoon dogs were deposited at the same time.

Depending on the stability of the genetic material of the virus and the animals, said Michael Imperiale, a virologist at the University of Michigan, “they could have been deposited there at potentially very different times.”

Yet Dr Arturo Casadevall, an immunologist at the Johns Hopkins Bloomberg School of Public Health who co-authored a recent study with Dr Imperiale examining the origin of the coronavirus, said the link between animal and viral material nonetheless adds to evidence of a natural overflow event.

“I would say it reinforces the zoonotic idea,” he said, “that is, the idea that it came from an animal at the market.”

Absent the actual animal that first spread the virus to humans, Dr. Casadevall said, assessing the origins of an outbreak would always involve weighing the odds. In this case, the animals sold on the market were removed before researchers began collecting samples in early 2020, making it impossible to find a culprit.

Tim Stearns, the dean of graduate and postgraduate studies at Rockefeller University in New York, said the latest discovery was “an interesting piece of the puzzle”, although he said it was “not in itself definitive and highlights the need for further investigation.”