- Victoria Gil
- Science Correspondent – BBC News
Scientists say there is “compelling evidence” that the Huanan Seafood and Wildlife Market, in China’s Wuhan, was the first epicenter of the COVID-19 outbreak.
On Tuesday, two studies reviewed by researchers were published, which included a re-examination of information about the first outbreak of the virus in the Chinese city.
One of these two studies shows that the first known cases were concentrated around this market.
The other study uses genetic information to track the timing of the outbreak, and points to two different mutations that passed to humans in November or early December 2019.
The authors of the two studies say that this evidence shows that SAR-CoV-2 virus was present in live mammals sold in the Huanan market in late 2019.
They add that it was transmitted to people who were working or shopping there in “two separate events”, during which the virus was transmitted from animal to human, causing infection.
One of the researchers involved, virologist Professor David Robertson, from the University of Glasgow, told BBC News he hoped the two studies would “correct the wrong record that the virus came from a lab”.
A two-year scientific effort on the virus that causes COVID-19 has led researchers to a deeper understanding of the virus and its origins.
This enabled them to address a major problem with early patient data: Of the hundreds of people hospitalized with COVID-19 in Wuhan, only about 50 had a direct, traceable link to the market.
Professor Robertson said: “That was really confusing, because most cases cannot be linked to the market. But after learning what we now know about the virus, we found what we expected – because many people develop only mild symptoms, remain in the community and transmit the virus to others, and this It makes it difficult to link severe cases together.”
Research on the geographical distribution of cases found that a large proportion of the first patients – who had no contact with the market, meaning they did not work or shop there – lived near it.
Professor Michael Worby, lead author on the study and a biologist from the University of Arizona, said this supports the idea that the market was the epicenter of the epidemic, with vendors infected first and triggering a “chain of infection among community members in the surrounding area.”
“In a city that covers more than 3,000 square miles, the probability of finding a home where the oldest cases of COVID-19 have formed is limited to an area consisting of a few apartment blocks with the Huanan Market next to it,” he added.
This study focused on the market itself. The scientists mapped the samples – taken by swabs of fluids in banks and market stalls – that tested positive for the virus.
“Most of the positive samples were around the southwest side of the market,” Professor Robertson explained. “This is where we knew species like raccoon dogs were being sold.”
“So we have confirmation that animals that we now know are susceptible to SAR-CoV-2, the virus that causes COVID-19, were sold there in late 2019,” he added.
Leak theory from lab
Over the past two years, the search for the origin of the deadly epidemic has transformed from a scientific investigation into a heated political controversy.
The topic has turned into a fierce international blame game – primarily between politicians in the US and China – over the theory that the virus may have leaked from the Wuhan Laboratory, at the Wuhan Institute of Virology.
Professor Stuart Neal, from King’s College London, said this hypothesis “cannot explain the data”.
“We are now fairly certain, based on the evidence we have, that it was an indirect event that occurred in the market,” he added.
Many scientists agree that crowded live animal markets provide an ideal point for new diseases to “pass” from animals to humans. In the 18 months before the epidemic began, a separate study showed that nearly 50,000 animals – from 38 different species – were sold in markets in Wuhan.
Prof Neil said the epidemic was likely the result of “unhygienic, brutal and unhygienic practices about which warnings have been given to the Chinese authorities”.
He added that the main risk of getting distracted by looking for someone in the lab to blame “is that we risk the possibility of this happening again, because we are focusing attention on the wrong problem.”
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