The COVID-19 pandemic likely began with a female vendor at a large Wuhan live animal market in China, according to a new analysis of accounts and research by a top virologist.

In this city of 11 million people, half of the early cases are linked to a place thats the size of a soccer field, Dr. Michael Worobey of the University of Arizona told The New York Times, referring to the Huanan Seafood Wholesale Market.

It becomes very difficult to explain that pattern if the outbreak didnt start at the market, he said.

Its also clear that live mammals susceptible to coronaviruses , including raccoon dogs, were sold at Huanan Market and three other live-animal markets in Wuhan before the pandemic, Worobey, a leading evolutionary virologist, wrote in his analysis published Thursday in the journal Science.

Worobeys analysis indicates that the pandemic wasnt triggered by a leak in a Chinese lab or, as a report from the World Health Organization concluded, by a Chinese accountant who lived miles from the market.

Worobey reached his conclusions after poring over information in medical journals and local accounts, and from interviews with people believed to have had the first two documented COVID-19 cases.

He said WHO got the timeline wrong and that the first person known to become ill was the vendor, who became symptomatic Dec. 11, 2019 three days before the accountant became symptomatic, Worobey wrote.

Some scientists support Worobeys conclusions, while other still speculate that the first infection could have occurred earlier, before the vendors case, the Times noted.

Jesse Bloom, a virologist at the Fred Hutchinson Cancer Research Center, told the newspaper: I dont disagree with the analysis. But I dont agree that any of the data are strong enough or complete enough to say anything very confidently , other than that the Huanan Seafood Market was clearly a super-spreading event.

Worobey fired back Thursday on Twitter after Stanford microbiologist David Relman who leans toward the lab-leak theory told The Washington Post that his analysis was based on fragmentary information and to a large degree, hearsay .

Worobey said Relmans casual dismissal of accounts and comments by Chinese doctors, scientists and, apparently COVID-19 patients was beyond disrespectful and that it was an anti-scientific attempt to disparage a position that doesnt support Relmans hypothesis of a lab leak.

Worobey has been open to other theories , indicating that he didnt analyze information with a bias. He signed a letter with 18 other scientists to Science in May calling for continued investigation into the origin of COVID-19 including the possibility of a lab leak.