It also floats a widely disputed theory that frozen food imported to China might have been the original source. Hewing closely to government assertions on COVID-19’s origin, the preprint by Gao and colleagues notes studies that have reported evidence of SARS-CoV-2 in other countries before it surfaced in Wuhan, making no mention of critiques that attribute that evidence to contamination. The authors call the market an “amplifier,” not the source, of SARS-CoV-2. But because all were from the environment, not the animals themselves, they assert that humans introduced the virus to the market.

In the new preprint, Gao and colleagues analyzed 1380 samples from 188 animals in the market and the environment, including sewer wells, the ground, feather removing machines, and “containers.” They found SARS-CoV-2 in 73 samples.

Led by George Gao of the Chinese Academy of Sciences and co-authored by 37 other scientists (one is from Canada), that research-which builds on data earlier leaked to the media but never officially published-offers the most detailed description yet of the environmental samples the Chinese Center for Disease Control and Prevention obtained at the Huanan Seafood Market between 1 January and 2 March 2020. Worobey and colleagues had hoped to release their preprints in the next week but sped up their plans, choosing a preprint server that posts without any delays, when the Chinese study was posted on 25 February on the Research Square site. “Together, these analyses provide dispositive evidence for the emergence of SARS-CoV-2 via the live wildlife trade and identify the Huanan market as the unambiguous epicenter of the COVID-19 pandemic,” they conclude. It also connects the specific stalls at the market where live animals were sold to environmental samples known to have tested positive for the virus. Their other study offers a geospatial analysis of the earliest human cases that pinpoints the market as the “epicenter” of SARS-CoV-2’s emergence, showing both lineages infected people who had links to the market or lived near it. In one study, Worobey and colleagues describe two subtly different lineages of SARS-CoV-2 that were found in people at the Huanan Seafood Market in late 2019, which they take as a sign that the virus jumped twice from animals to humans there. A more transparent analysis of the market’s genetic sampling data, in particular, might identify exactly which species of animals sold there carried the virus. But Worobey thinks further data could make that contention even less tenable. Skeptics of the natural origin theory maintain the market cluster could merely be a superspreader event touched off when a person infected with a lab-escaped coronavirus visited it. “They substantially move the needle on the origins in the direction of the market,” Hanage says. Evolutionary biologist William Hanage of Harvard University agrees these studies “will be taken as a blow” to the lab-leak hypothesis. “I have been brought closer to the zoonosis side with these preprints,” says Flo Débarre, an evolutionary biologist at the French national research agency, CNRS, who has followed the origin debate closely and not thrown her lot with either the natural-origin or the lab-leak camp. The studies were posted as preprints and are not peer reviewed, but scientists, biosecurity experts, journalists, and others are already intensely examining their details.

A third, largely Chinese effort details early signs of the coronavirus in environmental and animal samples from the market but suggests the virus was imported there, perhaps from outside the country-a conclusion the University of Arizona’s Michael Worobey, an evolutionary biologist who is a corresponding author of the two international studies, calls “a huge disconnect.” Two international efforts build the case that SARS-CoV-2 jumped to people from infected animals-a zoonotic leap-at the market, likely twice, at the end of 2019. The studies examine different aspects of the viral spread at the Huanan Seafood Market in Wuhan, China, the city where the first cases were detected. And although these new analyses don’t all reach the same conclusion for how COVID-19 was sparked, each undercuts the theory that the virus somehow escaped from the Wuhan Institute of Virology, long a focus of suspicions. Three new studies offer one indisputable conclusion about the origin of SARS-CoV-2: Despite the passage of 2 years and the Chinese government’s lack of transparency, data that can shed light on the pandemic’s greatest mystery still exist. Update, 26 July, 5 p.m.: Two of the three preprints covered below, one looking at early lineages of SARS-CoV-2 in Wuhan, China, and another doing a geospatial analysis of the earliest COVID-19 cases in China, were published by Science.

Covid origin