Three studies have been released providing multiple lines of evidence pointing to Huanan Seafood Market as the COVID-19 pandemic's origin, with no support for escape from a laboratory.
None of these studies have been peer-reviewed, however, and none provide a smoking gun to prove the market theory. Nevertheless, if verified, they do provide additional evidence that the original theory for the virus' origins in humans was the right one
In a world overflowing with conspiracy theories, the fact COVID-19 was first reported in Wuhan, the site of a major virology institute, was too tempting for many to resist. Claims the SARS-CoV-2 was either a bioweapon cooked up at Wuhan Institute of Virology, or created there as part of “gain of function research” and accidentally released have resurged on multiple occasions.
Most of the “evidence” used to support both claims has been refuted, but an alternative explanation has yet to be proven.
In one study placed online over the weekend, a team of scientists from 23 institutions examined locations where 156 people who caught COVID-19 in December 2019 lived or worked, followed by a larger group in early 2020 as the virus spread. The earliest cases are clustered close to the western end of the market, which is where most species capable of transmitting the virus were sold. The subsequent spread matches a pattern that would be expected if humans had first caught the disease from animals sold there.
A second preprint looked at the genetics of the first COVID-19 viral lineages, referred to as A and B. The lack of any transitional variant indicates "that these two lineages were the result of at least two separate cross-species transmission events into humans,” the authors conclude.
Both are considered to have occurred in late November or early December. There have been claims that COVID-19 was circulating well before these dates – but if this is true, the researchers believe, it would indicate even more examples of the disease jumping to humans, rather than these lineages having done so earlier.
Only lineage B, which has caused by far the most damage in the pandemic, was found among people associated with the Huanan market, while lineage A is more closely related to viruses found in Rhinolophus bats.
Nevertheless, the preprint reports early victims of lineage A lived near or had recently stayed near the market, a previously overlooked relevant finding. Theoretically, it might be possible for SARS-CoV-2 to have leaked from a lab twice, but this would require the lab to have been working with two substantially different versions of the virus and allow both to escape. Twin transfers from a reservoir in which coronaviruses are known to be circulating widely makes far more sense.
Although these studies used very different approaches, they shared some of the same authors, including Professor Michael Worobey of the University of Arizona who was first author on one and among the corresponding authors on the other.
“When you look at all of the evidence together, it’s an extraordinarily clear picture that the pandemic started at the Huanan market,” Worobey told the New York Times. He added to CNN; "It's no longer something that makes sense to imagine that this started any other way."
That's significant because Worobey was an author of a letter last year arguing the lab leak hypothesis deserved to be taken seriously.
Meanwhile, an unrelated preprint by researchers at the Chinese Center for Disease Control and Prevention released the day before reveals the results of swabs for SARS-CoV-2 taken at the market after it had been shut down. Numerous examples of viruses collected from surfaces and sewers provide near-perfect matches for samples taken from humans infected early in the pandemic, supporting the claim the virus was widespread there before anywhere else.
However, SARS-CoV-2 was not found in any of the animals taken from the market, which would have offered the near-definitive proof scientists have been seeking.
The origins of COVID-19 are now so politicized that no amount of evidence will convince some people. Others will accept nothing short of a clear finding of the animal host and the predecessor virus from which SARS-CoV-2 evolved. However, as virologists have repeatedly warned, tracing outbreaks of disease to animal hosts is usually a slow process, the fact a host hasn’t been found yet is entirely to be expected.
Moreover, shutting down the market and removing most animals before researchers arrived to connect genetic samples may have been wise in preventing further transmissions, but reduced the chance of finding a non-human host.
Nevertheless, even experts interviewed by the New York Times about the research, while open to the possibility the papers are correct, were unconvinced the case is settled.