Leading British and US scientists thought it was likely that Covid accidentally leaked from a laboratory but were concerned that further debate would harm science in China, emails show.
An email from Sir Jeremy Farrar, director of the Wellcome Trust, on February 2 2020 said that “a likely explanation” was that Covid had rapidly evolved from a Sars-like virus inside human tissue in a low-security lab.
The email, to Dr Anthony Fauci and Dr Francis Collins of the US National Institutes of Health, went on to say that such evolution may have “accidentally created a virus primed for rapid transmission between humans”.
Watch: Scientist claims to identify COVID patient zero
But a leading scientist told Sir Jeremy that “further debate would do unnecessary harm to science in general and science in China in particular”. Dr Collins, the former director of the US National Institutes of Health, warned it could damage “international harmony”.
Viscount Ridley, co-author of Viral: the search for the origin of Covid, said: “These emails show a lamentable lack of openness and transparency among Western scientists who appear to have been more interested in shutting down a hypothesis they thought was very plausible, for political reasons.”
In the emails, Sir Jeremy said that other scientists also believed the virus could not have evolved naturally. One such scientist was Professor Mike Farzan, of Scripps Research, the expert who discovered how the original Sars virus binds to human cells.
Scientists were particularly concerned by a part of Covid-19 called the furin cleavage site, a section of the spike protein which helps it enter cells and makes it so infectious to humans.
Summarising Professor Farzan’s concerns in an email, Sir Jeremy said: “He is bothered by the furin site and has a hard time (to) explain that as an event outside the lab, though there are possible ways in nature but highly unlikely.
“I think this becomes a question of how do you put all this together, whether you believe in this series of coincidences, what you know of the lab in Wuhan, how much could be in nature - accidental release or natural event? I am 70:30 or 60:40.”
Later emails showed that by February 4, Sir Jeremy had revised his estimate of a laboratory leak to 50:50, while Professor Eddie Holmes, of the University of Sydney, gave a 60:40 estimate in favour of an accidental release.
The emails also show that Bob Garry, of the University of Texas, was unconvinced that Covid-19 emerged naturally.
“I just can’t figure out how this gets accomplished in nature,” he said.
Professor Andrew Rambaut, from the University of Edinburgh, also said that furin cleavage site “strikes me as unusual”.
He added: “I think the only people with sufficient information or access to samples to address it would be the teams working in Wuhan.”
The new details came to light after members of the US Republican House Oversight Committee were granted access to the documents, after complaining that their content had been heavily redacted when released under Freedom of Information requests.
The emails were sent in response to a teleconference between 12 scientists including Sir Patrick Vallance, the Government's chief scientific adviser, on February 1.
The emails show that by February 2 2020, scientists were already trying to shut down the debate into the laboratory leak theory.
An email from Dr Ron Fouchier to Sir Jeremy said: “Further debate about such accusations would unnecessarily distract top researchers from their active duties and do unnecessary harm to science in general and science in China in particular.”
Dr Collins, former director of the NIH, replied to Sir Jeremy stating: “I share your view that a swift convening of experts in a confidence-inspiring framework is needed or the voices of conspiracy will quickly dominate, doing great potential harm to science and international harmony.”
Institutions which held the emails have repeatedly resisted efforts to publish their content.
The University of Edinburgh recently turned down an Freedom of Information request from The Telegraph asking to see Prof Rambaut’s replies, claiming “disclosure would be likely to endanger the physical or mental health and safety of individuals”.
James Comer, the Republican congressman who secured the unredacted emails, said it showed that experts like Dr Fauci had taken the Wuhan lab leak theory “much more seriously” than they had let on.
Sir Jeremy has been approached for comment but had not replied at the time of publication.
Watch: China says U.S. COVID origin report is unscientific