An animal market in the Chinese city of Wuhan was the epicenter of the Covid-19 pandemic and not an accident in a laboratory, according to two new studies published in the journal Science that analyzed “the geographical pattern” of the virus and the “genomic information” of the first cases.
The First article analyzed the geographic pattern of Covid cases in the first month of the outbreak, in December 2019, and showed that the first infections clustered around the Huanan market in the Chinese city of Wuhan.
The second investigation studied the genomic information of the first cases to analyze the early evolution of the virus, concluding that it was unlikely to circulate widely among humans before November 2019.
Both were previously published as preprints or “preprints”, but have now undergone scientific peer review and appear in a prestigious journal, according to the AFP news agency.
Michael Worobey of the University of Arizona and a co-author on both papers previously called in a letter for the scientific community to be more open to the idea that the virus was the result of a lab leak.
A related study suggests the #SARSCoV2 virus spilled over into people working or shopping in the Huanan market from two separate zoonotic transmissions, with lineages A and B circulating in animals prior to their introductions into humans. https://t.co/MUFCg1A0W9 @jepekar pic.twitter.com/FuJCZ2FIb2
—Science Magazine (@ScienceMagazine) July 26, 2022
But the findings led him “To the point where now I also think it’s just not possible that this virus was introduced in any other way than through the wildlife trade in the Wuhan market”he told reporters on a call.
Although the previous investigation had focused on the live animal market, investigators wanted more evidence to determine that it was actually the source of the outbreak, not its amplifier.
This required a neighborhood-scale study within Wuhan to make sure the virus was “zoonotic”that is, he jumped from animals to people.
The first study team used mapping tools to determine the location of most of the first 174 cases identified by the World Health Organization, finding that 155 of them were in Wuhan.
These cases were piling up around the marketand some of the first patients with no recent history of visiting the market lived nearby.
Mammals now known to be infectious, including red foxes, badgers and raccoon dogs, were all sold live on the market, according to the team.
The study concludes that it was unlikely that there was circulation in humans before November 2019
They also linked positive patient samples from early 2020 to those on the west side of the market, which was selling live or freshly butchered animals in late 2019.
The early cases contrasted with how it spread to the rest of the city between January and February, which researchers confirmed by drilling into the Weibo app’s social media log data.
“This tells us that the virus was not circulating cryptically,” Worobey said in a statement. “It really originated in that market and spread from there”.
The second study focused on resolving an apparent discrepancy in the early evolution of the virus.
The researchers conclude that Before February 2020, there were two lineages of the virus, A and Band that both were the result of two separate human transmission events, both in the Wuhan market.
Previous studies had suggested that lineage B had evolved from lineage A.
Under this scenario, there were probably other animal-to-human transmissions on the market that did not manifest as covid cases.
The study concludes that it was unlikely that there was circulation in humans before November 2019.
