The crackpot Covid theory that was dismissed by scientists – but is now the most likely scenario

Natural or man-made? Scientific fact or conspiracy theory? Species jump or lab leak? Both principal theories about the origin of Covid involve the transformation of a virus which, when it hit the human population, sparked a pandemic now three years old that has killed more than 6.8 million people worldwide.

But in that same period, another viral transformation has occurred – the shift of the theory that it started with a leak from a laboratory in Wuhan from fringe to establishment. Once shorthand for “social media nutter”, exploring the merits of the idea that Sars-CoV-2 emerged from Chinese state facilities where bats were being studied is now the stuff of polite dinner party conversation, accepted by establishment figures. In three years, what once appeared to be monolithic scientific consensus dismissing “lab leak” has given way to debate and dispute.

Just as the virus, in the natural spillover scenario, sprang from species to species, so the lab-leak theory has jumped from political group to group: marginalised to mainstream, kooky to conventional. Early on into the pandemic, the theory emerged that the virus had originated in the lab, which is a 40-minute drive from the Huanan wet market. Donald Trump said he believed it and others suggested the virus could have been engineered as a biological weapon. The Lancet medical journal rejected the theory, saying it was on a par with climate change denial and anti-vaxx theories. It printed a statement signed by 27 scientists asserting their solidarity with Chinese scientists and saying: “We stand together to strongly condemn conspiracy theories suggesting that Covid-19 does not have a natural origin.” Some scientists stuck their heads above the parapet and said there could be a case for the theory but for a long time they were in the minority.

Now, what once was vilified as xenophobic Trumpian hyperbole is today the sober conclusion of US government agencies in Joe Biden’s administration – including the FBI (which has sparked a diplomatic row with Beijing accusing Washington of political manipulation). Information, it seems, can evolve too. How did it happen?

It’s certainly been a journey. After all on April 18 2020, when president Donald Trump stood up at a press conference and declared that “the China virus” (or “kung flu” as he would soon label Covid) had emerged from a top-security bio-lab in Wuhan, he was also suggesting that injecting bleach might be a good idea. Pressed to reveal his sources, Trump demurred: “I can’t tell you that. I’m not allowed to tell you that.”

But his information certainly didn’t seem to come from America’s top infectious disease expert, Anthony Fauci, who immediately shot down the idea, saying Covid was “totally consistent with a jump of a species from an animal to a human”. Fauci was reflecting the view of an influential analysis of Covid’s DNA in Nature, published a month previously, which itself had come a few weeks after The Lancet’s statement.

When, less than a fortnight after Trump’s press conference, America’s Office of the Director of National Intelligence issued a highly unusual statement to note that “the Intelligence Community also concurs with the wide scientific consensus that the Covid-19 virus was not man made or genetically modified” it seemed the verdict was in. And it put Trump and loony-lab conspiracists on one side and right thinking people on the other.

Just a little over a year later, however, the picture had changed. Then, on May 21 2021, President Joe Biden ordered an intelligence review of the two leading Covid origin theories. This time Fauci was less quick to judge: “I keep an absolutely open mind that there may be other origins,” he said. “It could have been a lab leak.” Government agencies seemed suddenly equivocal. The director of America’s Centres for Disease Control and Prevention, Rochelle Walensky, described the lab theory as “one possibility”. Now the open letters from prominent scientists, including one who had worked closely with Shi Zhengli, director of the Wuhan lab, were calling for “hypotheses about both natural and laboratory spillovers [to be taken] seriously”. There wasn’t enough data to be conclusive, they insisted.

The carapace of certainty had cracked. And there had been certainty. A year before, for example, British scientists asked to respond to Trump’s assertions had rounded upon it. “The claim is false” and “outlandish” noted Dr Joshua Moon, at the University of Sussex, and reflected “a US which is abdicating its role in the international community”. Prof Brendan Wren at the London School of Hygiene & Tropical Medicine, noted that “it is generally accepted that the virus has mutated naturally. Pandemics happen naturally and it is unnecessary to invoke a conspiracy theory”. Dr Michael Head, at the University of Southampton, said it was “unhelpful for high-profile individuals to repeat the debunked conspiracy theories, as it undermines the public health response”.

But after Biden ordered his inquiry, the response was far more circumspect. “Knowing the origin of Sars-CoV-2 is essential in understanding what we need to do to prevent future pandemics,” noted Prof Lawrence Young at Warwick Medical School. “Much evidence points to the virus evolving in a bat and then accidentally spilling over into humans rather than originating from a laboratory.  But there are contrary theories …” Young even mentioned the report, which had just broken in May 2021, that three workers at the Wuhan lab had been hospitalised in November 2019, the month that until that point had been ground zero for the conspiracy community.

For it was on November 12 2019 that, a US Senate Report would later conclude, Wuhan lab workers appeared to report a biosecurity breach. A week later, the facility was paid an urgent visit by Ji Changzheng, technology safety and security director for the Chinese Academy of Sciences, to address a “complex and grave” situation. A few weeks later, a cluster of cases of a mysterious respiratory disease were reported in the city next door. For those with suspicious minds early in the pandemic, it all seemed to add up.

But they fought – and lost – to the emerging consensus. The fact that Wuhan’s cluster of cases originated around its market, stocked with live animals ripe for species-jump transmission to humans, seemed most compelling to scientists. In March came the influential paper in Nature which seemed to confirm matters, itself following hot on the heels of The Lancet’s group letter denouncing conspiracies. It seemed clear which side the angels were on.

Remarkably, that wasn’t the end. It emerged that the Lancet group letter had been drafted by Peter Daszak, president of EcoHealth Alliance, which had conducted work at the Wuhan lab. And a year after it was published, one of the signatories of the Nature paper, Ian Lipkin, confessed he’d reversed his opinion, having learned of “dangerous” studies with Dr Shi’s name on them done in “porous” labs. “That’s screwed up,” he told reporter Donald McNeil. “My view has changed.”

Sure, his new opinion flew against the face of a just-published WHO report, from February 2021, which noted the lab-leak theory was “extremely unlikely”. But by then he was not alone in his scepticism of official conclusions. Indeed, to many, the WHO producing such sweeping conclusions from a visit completely controlled by China was tantamount to a whitewash and suspicious in itself. The Biden administration said it had “deep concerns” with the report. Scientists, in a letter to the WHO, called for a new, full and “unrestricted” investigation. The tide was turning. Biden announced his intelligence investigation. And then nothing. In August 2021, Biden’s spooks told him they couldn’t be sure what happened. The trail had gone cold.

Yet the debate had changed. The lab-leak theory was no longer such a touchstone of lunacy, as once it had been portrayed. Certainly, debate continued, often on partisan lines. In early 2022 the animal transmission theory was given wings by a major paper identifying Wuhan’s market as the “epicentre” of the pandemic and was much-publicised by The New York Times. Six months later, senate Republicans released a report noting “most likely” origin of the coronavirus was a “research-related incident”. Now it is the Department of Energy, which oversees a network of labs in America, which has concluded that Covid-19 originated in a laboratory.

Like others it can’t be sure. Its conclusion is made with “low confidence”. But the fact it is made at all, without the sound of raspberries and calls for the tin-foil hats, is startling, given where debate started, with Donald Trump, and bleach injections, back in April 2020.

“This is how science works,” says Prof David Robertson at the University of Glasgow Centre for Virus Research. “We very happily … change our minds [depending on the evidence]. That’s literally what we do.” For his part, though, he says that the evidence now points more strongly than ever to a species-jump. “A virus in Laos [neighbouring China] has been found with an almost identical spike protein [to Covid]. Somehow a naturally infected bat has come into contact with another species, and that has ended up at the [Wuhan] market.” Can we be absolutely sure? “The problem now,” he says, “is that we’ll probably never know.”