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Home SCIENCE New studies say Wuhan market is only 'plausible' source of COVID-19 pandemic

New studies say Wuhan market is only ‘plausible’ source of COVID-19 pandemic

Not long after the World Health Organization and China released a report last year ruling out the possibility that the SARS-CoV-2 virus originated in a laboratory leak, scientists at leading research institutions around The world noted the dearth of published data and called for rigorous scientific investigation into the origins of the pandemic.

An international team of experts responded to that protest Tuesday with two companion articles published in the journal Science. Using different analytical approaches, both documents identify the Huanan Seafood Wholesale Market in Wuhan as the epicenter of the pandemic that has killed since more than 6.4 million people all over the world.

Although the exact species of the animal is not yet known, the authors conclude that SARS-CoV-2 was most likely present in animals sold on the market in late 2019 and jumped to human workers or buyers in at least two separate instances.

“In a city that covers more than 3,000 square miles, the area most likely to contain the home of someone who had one of the world’s first cases of COVID-19 was an area of ​​a few city blocks, with Huanan market right inside it,” michael worobeya virologist at the University of Arizona who co-authored one of the new studies said in a statement.

“All of this evidence tells us the same thing: It points directly to this particular market in the middle of Wuhan,” the study co-author echoed. christian andersen from the Scripps Research Institute in San Diego.

“Any other version, a lab leak for example, would have to explain all this other evidence and in my opinion,” he added, “that’s just not plausible.”

In the early days of the pandemic, before SARS-CoV-2 circulated widely in the US, Andersen wrote for the doctor. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, expressing concern that the new virus had characteristics of being engineered by humans.

As the research evolved, so did his thinking.

“I was pretty convinced of the lab leak myself until we dove into this very carefully and took a much closer look at it,” Andersen said. “Actually, the data points to this particular market.”

Worobey also had his doubts about the origin story of the Huanan market. He was one of 18 experts who published to an open letter last year in the journal Science that advocated further investigation into the possibility that the virus had inadvertently escaped from a research lab.

“I haven’t seen evidence that I can look at and say, ‘Oh, okay, this certainly disproves the accidental origin of the lab and makes it pretty much 100% certain that it was a natural event,'” he said at the time. “Until we’re onstage, both possibilities are viable.”

Worobey went on to make a detailed account of the first cases of what was then considered pneumonia of unknown origin. Hears reported in science than a 41-year-old accountant who had been identified as the first COVID-19 patient on December 2. 8 actually had a fever due to dental surgery. The accountant appeared to have contracted the coronavirus eight days later, but that was days after a Huanan market seafood vendor sought treatment for what was likely COVID-19.

The teams behind the new studies included more than 30 researchers from 20 different institutions around the world. They generally divided their work into two parts: one tracing the initial appearance of the virus in animals and people, and the other analyzing genomic data from the first cases.

In the first study, the team was able to analyze the location of almost all COVID-19 cases identified by the WHO in December 2019, 155 of which were in Wuhan. The sickest patients in that first month of the outbreak were all clustered around the market.

In January and February, as the virus spread, the highest concentrations of infections moved from the neighborhood surrounding the market to more densely populated areas of the city.

Additionally, swabs taken from surfaces in the market itself were much more likely to test positive from cages and stalls that sold live animals vulnerable to the coronavirus, including red foxes and raccoon dogs. Those animals were likely infected by bats or other farm animals known to harbor the coronavirus.

the second study examined the genomic sequence of the virus in the early days of the pandemic. The researchers identified two distinct lineages of SARS-CoV-2, suggesting that the virus jumped into the human population in two separate instances.

“Before embarking on this investigation, we were not very clear about how lineage A and lineage B were related to each other, and whether they had both occurred in or around the Huanan market,” he said. dr marc suchard, a biostatistician at UCLA Fielding School who worked on the study. The data showed that both versions of the virus circulated on the market, suggesting that there were at least two separate cases of successful transmission of the virus from animals to humans. “You’re about 60 times more likely to have multiple filings,” Suchard said.

The studies are an indirect response to a commission from the WHO report on the origins of the pandemic that was published in March 2021. Using data provided by China, the report ranked four possible scenarios for the genesis of the pandemic, from “extremely unlikely” to “very likely.”

That report identified the most likely cause of the pandemic as a viral jump from a host species to humans via an intermediate animal. An accidental release of virus from the Wuhan Institute of Virology or another laboratory was considered less likely.

The other two theories studied included a direct jump from an animal host to a human (“possible to probable”) and surface transmission from frozen food products (“possible”).

Almost as soon as the report was released, scientists around the world raised concerns. In May 2021, Science published the open letter from Worobey and researchers from Harvard, Yale, Stanford, and other leading institutions calling for further investigation.

Not that the report’s conclusions seemed implausible, they argued. The problem, the scientists wrote, was that the report did not appear to offer enough hard evidence to support any conclusions.

“In all respects, it was not a proper and detailed type of data presentation that would allow an outside scientist to come to an independent conclusion.” dr david relmanco-author of the letter and a professor of microbiology and immunology at Stanford University, told The Times when the letter was published.

WHO Director General Tedros Adhanom Ghebreyesus appeared to share similar concerns following the report’s release, offering the global organization’s resources to conduct a more robust investigation.

“Although the team concluded that a laboratory leak is the least likely hypothesis, this requires further investigation,” it said in a statement. speech to member states. “Let me state clearly that as far as the WHO is concerned, all scenarios are still on the table.”

A follow-up report published last month by a group of experts convened by the WHO said more work was still needed to understand whether the pandemic could have been caused by a laboratory accident.

Irrefutable proof is harder to come by in biology than in a field like math or physics, Andersen warned. However, he and his fellow co-authors who previously considered the lab leak hypothesis said they feel the currently available evidence points strongly in one direction.

Worobey agreed. The evidence he and his colleagues released Tuesday, he said, “has gotten me to the point where I also now believe it’s implausible that this virus was introduced in any way other than through the wildlife market trade.” of Huanan”.

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