It is “extremely unlikely” the novel coronavirus came from a laboratory incident in China, according to a joint mission investigating the origins of the pandemic.
Investigators believe the most likely cause of the initial outbreak was the virus jumping from an “intermediary host species” to humans.
It means future investigations will not focus on a laboratory incident as a potential cause of the outbreak.
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An international team of World Health Organisation (WHO) scientists, working with experts in China, has been researching how the COVID-19 pandemic began.
The team has visited key locations in Wuhan, where the first cases were reported, and spoken to patients, first responders and Chinese scientists.
Evidence so far suggests the novel coronavirus may have jumped from animals to humans, but the team told a news conference it is not yet sure exactly which animals it came from or where this occurred.
The hosts may have been bats or pangolins – and then jumped to another animal before coming into contact with humans – but samples of viruses found in these animals were not identical to SARS-CoV-2.
Investigators should now look at studying bats outside of China to see if they carry genetically similar viruses, the WHO’s Dr Peter Ben Embarek said.
China’s National Health Commission spokesperson Professor Liang Wannian also suggested more research is needed into whether felines could have hosted the virus.
“The susceptibility of mink and cats to SARS-CoV-2 suggests there may be additional animals, such as those belonging to the feline family, who may act as reservoirs for the virus. But there is not yet enough research to know for sure,” he said.
It is also thought likely the virus could have been transmitted from frozen food, according to Dr Embarek.
He added the virus could have emerged this way through “convoluted pathways that may have taken a long time and moved it across borders”.
Investigations have continued to focus on the Huanan wet market in Wuhan, which was linked to a cluster of initial cases.
The market had been selling frozen animal products but there were also vendors selling products from domesticated wildlife.
It is still thought to be one of the first clusters of cases, but Professor Liang said transmission was also happening in other areas of Wuhan at the time.
Scientists also revealed the novel coronavirus could have been circulating in regions outside Wuhan before the first reported cases of the outbreak.
Unpublished data suggests samples of SARS-CoV-2 were found several weeks before the first reported cases in Wuhan, Professor Liang said.
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However, he added there was no evidence that COVID was spreading in Wuhan before December 2019, when the first cases were reported, after officials looked at research samples, pharmaceutical sales and hospital records.
There was also no evidence of “large outbreaks” before December 2019 in Wuhan or elsewhere, Dr Embarek said.
Analysis: We’re not that much closer to understanding where the pandemic came from
By Tom Cheshire, Asia correspondent
The WHO came to Wuhan with four theories about the origins of COVID-19. They will leave China with three.
The four ideas were: that it jumped directly from animals to humans, that it spread via an intermediate host, that it was imported in from somewhere else, or that it came from a lab.
Out of those, only the lab leak has now been discounted as “extremely unlikely”. Further research into it will not be pursued – at least not by the WHO.
It has always been a contentious idea – one put forward by the administration of Donald Trump without much evidence and dismissed by others as a conspiracy theory.
But there was scientific merit in examining it. As one of the WHO investigators, Peter Ben Embarek, told me: accidents do happen and there are a number of virus laboratories in Wuhan. The WHO team had said they were not ruling it out.
After four weeks in China, though, the WHO has dismissed it – all 17 experts voted unanimously, according to another team member. That’s after visiting the Wuhan Institute of Virology and speaking with scientists there.
Sceptics will pour over the full WHO report explaining their reasoning.
As for the other three theories, we are not much closer to understanding where COVID came from.
Peter Ben Embarek said its transmission and circulation could have followed a long, convoluted path. And so too will the research.
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