New genetic data is giving new life to the hypothesis of a zoonotic origin of the Covid-19 pandemic, documenting DNA traces of raccoon dogs, civets and other mammals in a market in the Chinese city of Wuhan. These animals may have served as intermediate hosts in the transfer of SARS-CoV-2 from bats to humans.
The data was initially spotted on March 4 by French researcher Florence Débarre (CNRS) on the Gisaid international genomic database, but it was only a few days later that she realized their importance, as she told several newspapers. Posted online by researchers at the Chinese Center for Disease Control and Prevention (CDC) in late January, the sequences involved samples taken in early 2020 in Wuhan’s Huanan market. She shared her discovery with a group of virologists who had already analyzed clues suggesting that the pandemic originated from animal contamination at this market.
As first reported by The Atlanticthey soon discovered matches with the genome of the raccoon dog, a small carnivorous mammal resembling a raccoon, sold for its fur and meat. Science also mentions the presence of DNA from civets and other mammals. This work has not yet been made public, nor has the raw data behind it. But the World Health Organization (WHO) was informed of its existence on March 12. The UN body convened a meeting on Tuesday, March 14 of the commission studying the origin of the pandemic (SAGO), attended by the Chinese researchers who had made an initial analysis.
George Gao (Chinese Academy of Sciences, ex-CDC) had mentioned the data in February 2022 in a non-peer-reviewed manuscript that concluded that Huanan market was not the origin of the pandemic but a distributor of it – supporting the official Chinese line that the virus had a foreign origin. The article states that the virus was not detected “in any of the samples covering 18 animal species in the market.” It is still awaiting publication in a Nature journal which requires the raw data to be made available. This may have been the motivation for putting these sequences online in Gisaid. The Chinese team removed them after the SAGO meeting.
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Is the new data likely to put an end to the intense debate between the supporters of a zoonotic origin and those who believe in a leak from one of the laboratories studying the coronavirus in Wuhan is possible? Débarre did not wish to comment until the report she is working on with her colleagues is finalized. Michael Worobey (University of Arizona), who has collaborated on several studies pointing to the Wuhan market as the epicenter of the pandemic, also said he was waiting for their “forthcoming” publication to go into detail. Kristian Andersen (Scripps Research, La Jolla, California), who is also working on this report and has co-authored several papers ruling out a laboratory leak as the origin – called on his Chinese colleagues to make the Gisaid sequences available again and to collaborate on their analysis.
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