A scientist who has pored over public accounts of early Covid-19 cases in China reported on Thursday that an influential World Health Organisation inquiry had most likely got the early chronology of the pandemic wrong.

The new analysis suggests that the first known patient sickened with the coronavirus was a vendor in a large Wuhan animal market, not an accountant who lived many miles from it.

The report, published on Thursday in the prestigious journal Science, will revive, though certainly not settle, the debate over whether the pandemic started with a spillover from wildlife sold at the market, a leak from a Wuhan virology lab or some other way.

The search for the origins of the greatest public health catastrophe in a century has fuelled geopolitical battles, with few new facts emerging in recent months to resolve the question.

The scientist, Michael Worobey, a leading expert in tracing the evolution of viruses at the University of Arizona, came upon timeline discrepancies by combing through what had already been made public in medical journals, as well as video interviews in a Chinese news outlet with people believed to have the first two infections.

Dr Worobey argues that the vendor’s ties to the Huanan Seafood Wholesale Market, as well as a new analysis of the earliest hospitalised patients’ connections to the market, strongly suggest that the pandemic began there.

“In this city of 11 million people, half of the early cases are linked to a place that’s the size of a soccer field,” Dr Worobey said. “It becomes very difficult to explain that pattern if the outbreak didn’t start at the market.”

Several experts, including one of the pandemic investigators chosen by the WHO, said that Dr Worobey’s detective work was sound and that the first known case of Covid was most likely a seafood vendor.

But some of them also said the evidence was still insufficient to decisively settle the larger question of how the pandemic began.

They suggested that the virus probably infected a “patient zero” sometime before the vendor’s case and then reached critical mass to spread widely at the market. Studies of changes in the virus’s genome have suggested that the first infection happened in mid-November 2019, weeks before the vendor got sick.

“I don’t disagree with the analysis,” said Jesse Bloom, a virologist at the Fred Hutchinson Cancer Research Centre. “But I don’t 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.”

New York Times News Service