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BEIJING – Experts from the World Health Organization and China have quashed the controversial theory that the coronavirus had leaked from a Wuhan laboratory, suggesting instead that the Covid-19 virus likely infected humans from an intermediate animal host.
The possibility that Covid-19 could have resulted from a laboratory incident was one of four hypotheses the researchers investigated during their just-concluded mission to Wuhan, where Covid-19 was first discovered in December 2019.
But it was “extremely unlikely” and no further research was required on this theory, said Dr Peter Ben Embarek, head of the WHO-led mission, at a press conference that concluded the team’s 28-day visit yesterday.
Instead, more studies are needed looking at whether the virus could have made the leap to humans from frozen animal products, Dr. Embarek said, in an indication of the direction of future research investigating the origins of Covid-19. .
Professor Liang Wannian, an infectious disease expert at Tsinghua University and a member of the joint WHO-China team, said laboratories in Wuhan did not have samples of the Sars-CoV-2 virus before the outbreak, refuting conspiracy theories postulated by some, including former US President Donald Trump.
“If this virus does not exist, there is no way it will leak,” he said.
The WHO team arrived in Wuhan in the middle of last month and visited key places in the city, including the Wuhan Institute of Virology and the Huanan Seafood Market, where many of the first cases were discovered.
Aside from the laboratory leak hypothesis, the other three scenarios that the WHO-led team explored include the virus jumping directly from a host animal; infect humans through an intermediate animal species; and its transmission to the human population through frozen food products.
Referring to the Huanan market, Dr. Embarek said that the virus could have been introduced there “by a person who was infected and then spread to other people in the market – it could be a trader or visitor – but it could also be the introduction of a product “. ”.
He added that among the “most interesting products” on the market are frozen wild animals, including species known to be susceptible to such viruses.
“We know that the virus can persist and survive in these cold, frozen environments, but we don’t really understand whether the virus can be transmitted to humans and under what conditions this could happen,” said Dr. Embarek, adding that more was being done. studies necessary.
He added that work so far suggests that bats are a “natural reservoir” for the coronavirus, but the virus is unlikely to have made the leap directly to humans in Wuhan, as the city is nowhere near these bat habitats. .
The team examined other intermediate animal species that could have introduced the virus to the city, but no exact animal reservoir was found, they said.
The team’s full findings will be published in a report to come, but their initial statements will vindicate Chinese officials, who have long angered the possibility that the virus could have come from a laboratory and responded that Covid-19 could. have been introduced. Wuhan through cold chain logistics and frozen food products.
Professor Liang also said that the team had examined hospital data and patient and drug records, which do not indicate that there was widespread transmission of Covid-19 in Wuhan before the first cases were discovered in December 2019.
The team had also reviewed unpublished studies from different countries that suggested the virus was circulating in other countries weeks before it was discovered in Wuhan, Professor Liang said.
Team member Marion Koopmans, a virologist at Erasmus University Medical Center in the Netherlands, said these studies did not provide “complete evidence” that the virus might have been circulating elsewhere, but could give an indication for further research. .
“So in the next step … we really should go and look for evidence of an earlier circulation, wherever it is indicated,” said Professor Koopmans.
Key results
Researchers from the World Health Organization and China explored four hypotheses related to the origin of Covid-19:
1. Direct zoonotic spill of coronavirus from an animal reservoir to humans.
2. Introduction of the virus through an intermediate animal host, where the virus could adapt or circulate before making the leap to humans.
3. Food-related transmission routes, or cold chain and frozen food products that act as a transmission surface for the virus to the human population.
4. A leak or escape from a laboratory.
Your key findings
– The WHO-led team said the possibility of Covid-19 as a result of a laboratory leak was “extremely unlikely.”
– The initial spread of Covid-19 in Wuhan in December 2019, with some sporadic cases at first and then small outbreaks in groups, is a “classic picture” of the start of an emerging outbreak.
– There is no evidence of widespread community transmission of Covid-19 before December 2019, when the first cases were discovered in Wuhan.
– Most likely, the virus was introduced into humans through an intermediate host animal, although the researchers were unable to identify an exact species.
Whats Next?
A full report describing the team’s findings and recommendations will be published. But the team gave indications for more lines of study:
– Study how the virus can infect humans from frozen food.
– Monitoring the supply chain of frozen animal products present in the Huanan market, to identify a possible animal host for the coronavirus.
– Expand the search globally to look for evidence of Covid-19 circulation before December 2019.
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