All hypotheses into the origins of the virus that causes Covid-19 “remain on the table”, global health leaders have said as they called for more research into whether or not the virus could have entered the human population as a result of a laboratory leak.
The World Health Organisation (WHO) said that “no stone will be left unturned” as it continues its probe into where the virus came from.
The comments come as the team investigating the origins of the virus published its initial report.
Researchers previously outlined initial findings after a visit to Wuhan in China.
China has faced claims that the Wuhan Institute of Virology could be the suspected source of the Covid-19 virus.
The team of experts from WHO and China said in February the virus which causes Covid-19 – SarS-CoV-2 is “extremely unlikely” to have entered the human population as a result of a laboratory-related incident.
But as the report was published, Dr Tedros Adhanom Ghebreyesus, director general of the WHO, said: “The team visited several laboratories in Wuhan and considered the possibility that the virus entered the human population as a result of a laboratory incident.
“However, I do not believe that this assessment was extensive enough.
“Further data and studies will be needed to reach more robust conclusions.
“Although the team has concluded that a laboratory leak is the least likely hypothesis, this requires further investigation, potentially with additional missions involving specialist experts, which I am ready to deploy.
“Let me say clearly that as far as WHO is concerned all hypotheses remain on the table.”
Investigators looked at four hypotheses when examining the possible origins of the virus:
– Direct transmission from an animal species into the human population.
– The introduction of the virus from an intermediary host species through another animal species “potentially closer to humans” where the virus could adapt, circulate and then jump to humans.
– The food chain, in particular the potential for frozen products acting as a “surface” for the transmission of the virus.
– A lab-related incident.
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The report concluded that the introduction of the virus from an intermediate host is the most likely scenario – which means the virus “jumped” from one species to another, and then jumped from the second species to humans.
It also suggests that the virus was circulating for several weeks before it was initially detected.
The authors wrote: “Some of the suspected positive samples were detected even earlier than the first case in Wuhan, suggesting the possibility of missed circulation in other countries.”
Dr Tedros added: “This report is a very important beginning, but it is not the end. We have not yet found the source of the virus, and we must continue to follow the science and leave no stone unturned as we do.
“Finding the origin of a virus takes time and we owe it to the world to find the source so we can collectively take steps to reduce the risk of this happening again. No single research trip can provide all the answers.”
In a press briefing, Dr Peter Ben Embarek, who leads the team of experts from WHO, was asked about Dr Tedros saying the assessment of laboratories was not “extensive enough”.
Dr Embarek said: “We looked at the different hypotheses as I outlined earlier, among others the lab incident possibility, this is the first time that we have been able to discuss openly this possibility.
“Initially it was just speculation all over the place as you remember throughout 2020.
“Now we have a process to discuss it. We’ve put it in our report. It has been assessed.”
He said that due to it not being the “key or main focus” it did not receive the “same depth of attention and work” as the other hypotheses.
Dr Embarek said the assessment was that it was not something where they could see a “strong indication” that it should be looked into.
“And therefore it was ranked as the least likely, so to speak, of the four possible pathways.
“Not saying that it was impossible, but not the one we would start initially going deeper in to and focusing our attention on.
“But this being said, of course if others and if there is a need to further explore this and potentially other hypotheses, of course we will continue to look into these hypotheses,” he said.
Dr Embarek was also asked about the possibility the virus originated outside of China.
He said it is “perfectly possible” that there were earlier sporadic cases circulating in and around Wuhan as far back as October 2019, with some of the cases potentially travelling and transmitting the virus abroad.
“Don’t forget that Wuhan was a major international hub at the time with direct flights every day to most parts of the world, most big capitals of the world.
“So that earlier move of the virus outside of the area could potentially be explained in that way,” he said.
He added: “The current thinking is still that we are looking at the start in and around Wuhan and moving backwards trying to find out how it came there, and whether it came from another part of China or elsewhere.
“That will depend on the further studies and research.”
Dr Embarek said that because of the suspicion of certain bat species being the host of the virus, and having found other relatively close virus strains to Sars-CoV-2 in the region and South East Asia in general where these bats are living, it is a “strong indication” that that is where the source is.
Since the virus was first detected in December 2019, there have been more than 127 million cases around the globe and 2.8 million deaths.
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