At the end of 2019, there were no bats or pangolins in the Huanan market in Wuhan. But there were a large number of animals of all kinds, some of which, such as the raccoon dog and the palm civet, were probably carrying and transmitting SARS-CoV-2, the virus responsible for the Covid-19 pandemic. This is confirmed by an analysis of genetic data carried out by an international team under the direction of Florence Débarre, of the Institute of Ecology and Environmental Sciences (CNRS/Sorbonne University/UPEC/IRD/INRAE), and published on Thursday 19 September in the American journal cell.
The French researcher had discovered, in March 2023, part of the data in question, published online in the Gisaid database by a Chinese team, which had taken environmental samples from the Wuhan market in early 2020, shortly after its closure. The sudden publicity surrounding this data led the Chinese researchers to publish it online in full and to hastily publish an initial analysis in Nature.
They confirmed the presence of raccoon dogs and other animals sold illegally, and samples positive for SARS-CoV-2. In fact, as early as January 2020, George Gao, respected director of the Chinese Center for Disease Control and Prevention (CDC), indicated, based on these initial analyses, that he strongly suspected that the epidemic was linked to the trade in wild animals in this market.
In June 2021, a study conducted before the pandemic to study the circulation of ticks, published in Scientific Reports, confirmed the illegal presence of raccoon dogs at the end of 2019. But in the meantime, the Chinese authorities, accused by Donald Trump, had pushed another hypothesis, that of an importation of the virus through frozen meat.
Is this why George Gao was more cautious in his later publications? The analysis presented by his team in Nature In 2023, they highlighted a possible bias in the collection of samples and pointed out that the presence of the virus and the genetic traces of these animals did not prove that they were infected with SARS-CoV-2. If this were the case, it was still possible that they had been contaminated by sick humans, and not the other way around, they insisted, believing that the market could only have been an amplifier of the spread of the virus, and not the starting point. origin of the pandemic.
“Accumulating evidence”
The study published in cell comes to fine-tune this undecided panorama. “With this data, as in 2023, it is not possible to specify where the virus came from and whether the animals were infected. says Florence Débarre. However, the pattern observed is what would be expected if infected animals were present in this market. » With his colleagues, he also conducted a comparison of the SARS-CoV-2 lineages detected in the samples with those found in the first known human cases infected with the virus. “Early diversity of the virus is represented in the market, which is consistent with a market-related origin”resume.
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