Cold-chain transmission
The mission followed months of negotiation with a defensive China to facilitate and cooperate with the probe. Stung by criticism that it initially covered up the extent of the crisis, Chinese state media and officials have promoted the theory that the virus didn’t start in China, but was brought in. The WHO’S validation of a potential cold-chain transmission route is likely to bolster those efforts.
The team studied tens of thousands of patient samples from Wuhan prior to the emergence of sick people in 2019. There was no evidence of significant outbreaks in China before December 2019, WHO officials said.
The lack of a clear pathway from bats to humans had stoked speculation - refuted by many scientists - that the virus might have escaped from the Wuhan Institute of Virology, home to a maximum bio-containment laboratory that studies bat-borne coronaviruses.
Members of the WHO mission visited the lab last week and asked Shi Zhengli, who has collected and analysed these viruses for more than a decade, about the research and the earliest known coronavirus cases.
“We embarked on a very detailed and profound search for other cases that may have been missed early on in 2019,” said Ben Embarek. “The conclusion was we did not find evidence of large outbreaks that could be related to cases of Covid-19 prior to December 2019 in Wuhan or elsewhere.”
The panel, comprising 17 Chinese and 17 international experts, looked for clues to understand how Sars-cov-2 whose closest known relative came from bats 1,000 miles away - spread explosively in Wuhan before causing the worst contagion in more than a century.
Liang Wannian, an expert with China’s National Health Commission, said there had been no substantial spread of the virus in the city before late 2019 outbreak. “This indicates the possibility of the missed reported circulation in other regions,” Liang, the Chinese lead of the team convened by the WHO, said. Liang said the team believes the virus originated in an animal, “but the reservoir host remains to be identified”.