A pair of studies released over the weekend allegedly provides new evidence in support of the theory that COVID-19 originated in a wet market in Wuhan, China, in late 2019.
The studies, which have yet to be peer-reviewed or published in any scientific journals, were co-authored by scientists from the U.S., the U.K., South Korea, Singapore, the Netherlands, Malaysia, Canada, Belgium and Australia, as per The Guardian.
Using spatial analysis, one of the studies found that 156 cases in December 2019 clustered around the Huanan Seafood Wholesale Market, which has long been reported as the epicenter of the initial SARS-CoV-2 outbreak. Previously discovered evidence specifically pointed to 10 stalls in the market which sold live animals, according to a World Health Organization (WHO) report published last March.
The researchers behind the latest studies mapped five positive samples to a single Hunan market stall, but not to the live animals it sold. Instead, genetic material of the coronavirus was detected on various surfaces and objects at the stall, including two carts used to move animals around, a cage for live animals and a machine that removes feathers and hair.
Robert Garry, a professor of microbiology and immunology at Tulane Medical School, told CNN that these findings are “as close to having the virus in an animal as you can get.”
“Geographical clustering of the earliest known COVID-19 cases and the proximity of positive environmental samples to live-animal vendors suggest that the Huanan Seafood Wholesale Market in Wuhan was the site of origin of the COVID-19 pandemic,” the summary of the first study stated.
The second study analyzed the origin and pattern of SARS-CoV-2’s genomic diversity early on in the pandemic. Researchers found that two major viral lineages — designated as A and B in their study — emerged from at least two separate cross-species transmission events into humans.
Evidence suggests that lineage B viruses crossed over to humans first, with the very first transmission occurring in late November or early December 2019. A raccoon dog or another mammal, according to the researchers, may have served as the intermediate host during the earliest transmissions.
Michael Worobey, the head of ecology and evolutionary biology at the University of Arizona, said the studies offer “the strongest evidence yet” of COVID-19’s zoonotic origins. “It’s no longer something that makes sense to imagine that this started any other way,” he told CNN.
The new studies undermine the lab leak theory, which claims that SARS-CoV-2 was created in a laboratory in Wuhan. While the 2021 WHO report suggested that it likely originated in the Huanan market, Director-General Dr. Tedros Adhanom Ghebreyesus refused to “eliminate any option as a possibility” at the time, as per Newsweek.
The lab leak theory, which was strongly backed by former President Donald Trump, regained credence last year after President Joe Biden ordered the U.S. intelligence community to run a closer review of COVID-19’s origins. After 90 days, the community failed to trace a definitive origin but concluded that it “was not developed as a biological weapon.”
The new studies complement a separate study conducted by scientists at the Chinese Center for Disease Control and Prevention. The study, which was published online on Friday, investigated environmental samples from the Huanan market early on in the COVID-19 outbreak. Scientists found lineages A and B in the samples, suggesting that there could have been at least two spillover events within the market.
“I think we’ve cracked this case,” Joel Wertheim, a virologist at the University of California, San Diego and co-author of the studies, told The New York Times. Jeremy Kamil, a virologist at Louisiana State University Health Shreveport, commented that “The beauty of it is how simply it all adds up now.”