This is the conclusion of a pair of studies, published yesterday, that firstly show that the earliest cases of COVID-19 were clustered around the market and secondly use genetic information to track the coronavirus’s progression. According to the researchers, SARS-CoV-2 — the virus that causes Covid — was most likely present in live mammals that were sold at the Huanan market at the end of 2019. The outbreak began, they explained, when two variants of the virus separately “spilled over” from the animal into the human population in either November or early December 2019.
Paper author and virologist Professor David Robertson of the University of Glasgow told BBC News that he hoped the findings would finally “correct the false record that the virus came from a lab”.
The new studies, he explained, have allowed researchers to resolve a standing mystery in the earliest patient data from the pandemic — that of why, of the hundreds of people who were initially hospitalised with COVID-19 in Wuhan, only 50 could be traced to the market.
Prof. Robertson added: “That was really puzzling that most cases could not be linked to the market — but knowing what we know about the virus now, it’s exactly what we would expect.
“Many people only get very mildly ill, so they would be out in the community transmitting the virus to others and the severe cases would be hard to link to each other.”
Furthermore, the researchers explained, a large proportion of the early Covid patients that had no connection to the market itself — having neither shopped nor worked there — did in fact turn out to live close by.
Thus, the market does appear to have been the epicentre of the epidemic, paper author and biologist Professor Michael Worobey of the University of Arizona told BBC News.
Sellers and workers attending the market, he added, would have contracted the virus first, leading to a “chain of infections among community members in the surrounding area.
In a city covering more than 3,000 square miles, the area with the highest probability of containing the home of someone who had one of the earliest Covid-19 cases in the world was an area of a few city blocks — with the Huanan market smack dab inside it.”
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The theory that the COVID-19 pandemic was the result of a containment leak from a lab at the Wuhan Institute of Virology has been the subject of considerable scientific and political debate for two years now.
However, virologist Professor Stuart Neil of King’s College London — who was not involved in the recent studies — told BBC News that this hypothesis simply “can’t explain the data”.
He added: “We’re not as sure as we can be, based on the fragmentary evidence we do have, that this was a spillover event that happened in the market.”
Experts agree that crowded live animal markets provide the ideal environment for the so-called zoonotic spillover of diseases from animals into humans.
Furthermore, investigations have indicated that nearly 50,000 animals from 38 individual species were sold at markets across Wuhan in the 18 months preceding the pandemic.
The pandemic, Prof. Neil said, was likely a side-effect of this “unhealthy, cruel and unhygienic practice that Chinese authorities had been warned about”.
He warned that the danger of the endurance of the lab leak theory “is that we run the risk of letting this happen again because we’ve focused on the wrong problem.”
The full findings of both studies were published in the journal Science.