A group of scientists say they have evidence suggesting COVID-19 emerged from animals and jumped to humans at a market in Wuhan, China. They have also dismissed theories linking the deadly virus to a lab leak. The researchers studied DNA samples from hundreds of sources and found circumstantial evidence connecting the virus to the wildlife trade at the Huanan Seafood Wholesale Market, according to a study published in the journal Cell.
The scientists looked at genetic information gathered from the market at the beginning of 2020. Their findings showed that the genetic diversity of SARS-CoV-2, which is linked to the market, supported the theory that the virus emerged there. Higher levels of the virus were found near and inside a wildlife stall, which contained animal DNA in all SARS-CoV-2-positive samples. The animals identified included civets, bamboo rats, and raccoon dogs, all previously thought to be possible intermediate hosts.
Angie Rasmussen, a co-author of the study and a virologist at Canada's University of Saskatchewan's Vaccine and Infection Disease Organization, said the virus likely spread through animals sold at the market, with genetic evidence suggesting the same. “It's very difficult to explain any other way, besides that the virus was brought there with those live animals and it spilled over, twice actually, into the human population at the market,” Rasmussen said.
In March 2020, the World Health Organization outlined two main theories with respect to the origins of the COVID-19 pandemic. One theory suggested the virus transmitted from an infected animal to a human, most likely at the market, while the other proposed it leaked from the Wuhan Institute of Virology.
While the study does not confirm the animals in those areas were infected, the proximity of COVID-19 samples to their DNA suggests a strong likelihood that these animals were carriers. Commenting on the study, Dr. Lisa Barrett, an infectious disease expert from Dalhousie University, said it could help prepare for future pandemic responses.
Rasmussen and her team's earlier research, alongside other peer-reviewed studies, had already pointed to the Huanan Market as the most likely site of the virus's jump to humans, particularly linked to the live animal trade.
The breakthrough came in March 2023 when a significant dataset, previously used by Chinese scientists for their own research, became available online. This allowed Rasmussen's team to re-analyse the genetic samples taken from swabs at the market, uncovering new clues that further strengthen the animal market theory. Rasmussen said, “None of that can be explained with a lab leak.”
For a lab leak scenario to be plausible, someone would have had to contract the virus at the Wuhan Institute of Virology and then visit the market without spreading it to others, and the same would need to happen for a second strain of the virus. Rasmussen argued the likelihood of this happening is minimal, adding that resources should focus on the more likely scenario of animal-to-human transmission, rather than the unsupported lab leak theory.
Rasmussen and her team have faced significant backlash online from lab leak supporters, with accusations that they are attempting to cover up the “real story,” according to CBC News. Despite the criticism, Rasmussen maintains that their research is based on solid scientific evidence. “We're accused of conducting a propaganda campaign essentially to cover up the real story of a lab leak. But that's simply not true,” she said.
