By Anne-Gaëlle Moulun

The origin of the COVID-19 pandemic has sparked much debate, and various hypotheses have been put forward.

"My colleagues and I have examined the issue with an open mind, taking into account all possible hypotheses. The laboratory origin hypothesis was legitimate and deserved to be investigated," said Florence Débarre, a research director at French National Center for Scientific Research at the Institute of Ecology and Environmental Sciences in Paris, France. Nevertheless, research carried out as part of a large international collaboration points more toward an animal origin at the Wuhan market in China.

"We studied data from environmental samples taken at the Huanan market in Wuhan shortly after its closure in early 2020," said Débarre. The data were shared by the Chinese Center for Disease Control and Prevention on open and public databases. They include the raw genetic sequences of more than 800 samples collected at the Huanan market, on cages and carts, on the floors and walls of the stalls, and in the pipes and sewers.

These data allowed researchers to highlight the co-presence at this location of genetic material from the SARS-CoV-2 virus and certain wild animals. Masked palm civets, which are wild canids similar to foxes, with a dark facial mask similar to that of raccoons, and civets, small carnivorous mammals close to mongooses, were at the site.

"These species were already involved in the emergence of the SARS epidemic in the early 2000s and considered to facilitate the transmission of the virus from animals to humans," said Débarre.

These animals were identified based on their DNA and located in the southwest part of the market, which is also a hotspot where many samples tested positive for SARS-CoV-2.

"There is a particular stall where the virus and the animals were found," she said.

Since the data used are based on environmental samples, it is not possible to formally demonstrate that the animals were infected, but the discovery of virus samples located in the same place as the genetic material of these animals suggests that they were.

"There were samples taken from some animals at the market, but not from others, as they had already been evacuated when the sampling services arrived," said Débarre. These results add to a large body of evidence that all points in the same direction: an animal origin at the Wuhan market.

The team also found other zoonotic viruses, such as avian flu. "This study confirms that live animal markets pose a high health risk, especially when they are at the heart of urban centers," said Débarre. "It can provide avenues for prevention, particularly by limiting interactions between humans and wild fauna," she concluded.