The international team homed in on raccoon dogs — fluffy mammals related to foxes and sold for meat and fur — because of how much of the animals’ genetic material was found in the key swab from the cart and because they are known to spread the virus. They said their findings were consistent with that animal harboring the virus, which originated in bats, and passing it to humans at the market.
“This isn’t an infected animal,” said Joel Wertheim, an evolutionary biologist at the University of California, San Diego and a co-author of the report, referring to the new genetic data. “But this is the closest you can get without having the animal in front of you.”
The report, though, also offered the most concrete evidence to date of other animals susceptible to the virus being sold at the market, noted Kristian Andersen, a virologist at the Scripps Research Institute in La Jolla, Calif., and a co-author of the report. Genetic material from those animals — like the masked palm civet, a small Asian mammal that was implicated in the SARS outbreak two decades ago — was also found in swabs that were positive for the coronavirus.
“It’s literally Disney Land for zoonotic transfer,” said Joseph DeRisi, a professor of biochemistry at the University of California, San Francisco, and president of the Chan Zuckerberg Biohub, referring to the range of animals documented in the report.
A number of other swabs at the market found large quantities of human genetic material — an indication, the report said, of certain virus samples likely being shed by infected people. Many of the earliest known Covid patients worked or shopped at the market.
Still other positive swabs, the report said, were dominated by genetic material from animals that are not believed to be susceptible to the virus. A sample taken from a fish packaging surface, for example, contained a lot of fish genetic material. That virus was likely to have been deposited by a person, scientists said, illustrating that substantial amounts of animal genetic material did not necessarily mean that animals had produced the virus there.
Citing those findings, some scientists said that the kinds of swabs analyzed in the report simply could not offer conclusive proof of an infected animal.
