The study states the first patient worked at Huanan live animal market in the Chinese city and began feeling ill on 11 December 2019.
Michael Worobey, a virus expert from the University of Arizona, asserts in the paper a cluster of early symptomatic cases at Huanan Market – specifically the western section where raccoon dogs (which are susceptible to coronaviruses) were caged – “provides strong evidence of a live-animal market origin of the pandemic”.
Crucially, the report says, “the now famous ‘earliest’ Covid-19 case, a 41-year-old male accountant, who lived 30km (18.6 miles) south of Huanan Market and had no connection to it – illness onset reported as 8 December – appears to have become ill with Covid-19 considerably later.
“When interviewed, he reported that his Covid-19 symptoms started with a fever on 16 December; the 8 December illness was a dental problem related to baby teeth retained into adulthood. He believed that he may have been infected in a hospital (presumably during his dental emergency) or on the subway during his commute.”
The evolutionary biologist explains in his research paper, published in the journal Science, that this patient’s “symptom onset came after multiple cases in workers at Huanan Market, making a female seafood vendor there the earliest known case, with illness onset 11 December”.
The report details how officials picked up on a spate of mysterious pneumonia cases in Wuhan hospitals towards the end of December after several patients who had undergone CT scans were found with the same unusual lesions in their lungs.
At the same time, public health authorities in China were being alerted to the cases, and by 1 January 2020, Huanan Market had been closed and disinfected.
Dr Worobey warned that a failure to sample viruses from nearby animals at the time of the emergence of the virus may mean it is never possible to establish where the animal spillover occurred, though analysis of spatial patterns of early cases and additional genomic data could yet definitively prove the market as the origin of Covid-19. “Preventing future pandemics depends on this effort,” he said.
Chinese researchers collected hundreds of environmental samples immediately after the coronavirus was found, but it is unclear how many people or animals were tested.
Earlier this year, the World Health Organisation (WHO) sent a team of experts to Wuhan to probe what might have triggered the pandemic now blamed for more than 5 million deaths worldwide.
In their analysis, published in March, the WHO team concluded the virus probably jumped to humans from animals, and they described the possibility of a laboratory leak as “extremely unlikely”.
China responded saying that officials should “concentrate on other possible avenues that may help trace the origin” of Covid-19 and suggested studies should be pursued in other countries.