The CIA’s claim that the Covid-19 virus probably emerged from a Chinese laboratory leak has revived a fierce five-year battle over the pandemic’s origins.
Several US agencies and some scientists have proposed the lab leak theory over the past few years. But other experts insist there are good reasons to think the devastating pathogen emerged from a market where animals are traded.
Beijing has never fully co-operated with international investigators, impeding the search for a definitive answer. But scientists continue their quest to establish the causes of a global health crisis that killed millions of people, caused trillions of dollars of economic damage and increased fears over the risks of virus research.
What is the global balance of opinion on Covid’s origins?
The CIA said on Saturday that the Sars-Cov-2 coronavirus was “more likely” to have a “research-related” origin than a natural one.
But the CIA said it had “low confidence” in its conclusion, which came after its new director John Ratcliffe took office and urged the agency to “get off the sidelines” in its analysis on the pathogen’s origins. Its assessment gave no indications of having drawn on new intelligence and was the product of a review ordered as President Joe Biden prepared to leave office.
The CIA’s statement is the latest from US politicians and agencies that lean towards the lab leak theory. Some Republican lawmakers have used the hypothesis as part of a broader critique of China’s handling of the outbreak. Beijing has denied that either the Wuhan Institute of Virology, a leading centre for coronavirus research, or the Wuhan Center for Disease Prevention & Control were the initial virus source.
Asked about the CIA statement this week, China’s foreign ministry said the US should “stop politicising and weaponising origins-tracing”.
Many authorities internationally have yet to take a strong position on Covid’s origins, while stressing that they back WHO efforts to establish it. The UK’s health ministry said a “robust, transparent and science-led review” would “better prevent” future pandemics.
The WHO’s relations with Beijing deteriorated when Chinese officials did not allow the health body to probe Covid’s origins thoroughly. This month the organisation said it was a “moral and scientific imperative” for China to offer the necessary data and access.
Why is there support for the lab leak theory?
Its advocates believe that if a potent new coronavirus appears in a city that was a centre for research into such pathogens, then a lab was probably the origin.
The Wuhan institute’s work reflected a growing focus on the threat posed by diseases of animal origin. Such zoonotic coronaviruses are thought to have caused the Sars and Mers outbreaks in 2002 and 2012. The institute sometimes worked with US partners on US government-funded projects, such as 2015 “gain-of-function” experiments that made coronaviruses more deadly for research purposes.
The lab leak idea has spawned various sub-theories. One is that Sars-Cov-2 was being investigated by researchers having been gathered from a bat or other wild animal. Another is that the pathogen was created by modifying a natural coronavirus. This could have been done either by a process of artificially accelerated evolution known as serial passaging, or by genetic engineering.
Proponents of the lab leak hypothesis acknowledge the lack of supporting proof, but argue this is impossible to gather without Chinese co-operation.
“There is not a smoking gun, but there’s a gun laying on the table and it’s warm to the touch,” said Jamie Metzl, a former member of a WHO advisory committee on genome editing. “There is all of this circumstantial evidence.”
What do the lab leak theory’s critics say?
Many scientists still favour a scenario that Covid, like other coronaviruses, emerged in animals and then passed to humans. According to this model, the likely starting point was contact between wild creatures and humans in a Wuhan wet market where early Covid cases were identified.
The theory found support in research published last year on environmental samples taken from Huanan Seafood Market in the central Chinese city in January 2020. It pinpointed a stall where all the Sars-Cov-2 positive swabs contained traces of wildlife DNA too, showing both animals and virus were present at the same location. The samples included genetic material from species such as raccoon dogs, civets and bamboo rats. All these creatures had been identified as possible sources of virus transmission to humans.
“Multiple plausible intermediate hosts of Sars-Cov-2 were present at the exact site within Wuhan to which Covid-19 was first epidemiologically linked,” the researchers wrote.
Critics allege the market origin theory is flawed. They say it gives too little weight to reports of human Covid cases as early as November 2019. The market hypothesis also includes the contested suggestion that there were at least two separate spillover events there from animals to humans, helping seed an epidemic.
The scientists behind last year’s study say neither of these points undermines the idea that the market was the source of Covid. They contend that Sars-Cov-2 genetic material in the January 2020 samples could have been deposited weeks before, consistent with the reports of Covid cases in November 2019. Prof Florence Débarre, an evolutionary biologist and co-author of the research, said a market origin was “likely whether or not there were multiple spillovers”.
The CIA had not provided corroborating information for its lab leak assessment, Débarre noted, adding: “I hope that the data and logic leading to the conclusion of the various elements of the US intelligence community will one day be made public.”
Has the debate influenced ‘gain of function’ research?
Gain of function research involves manipulating pathogens to probe their behaviour by enhancing properties such as transmissibility and ability to cause disease. The work may be done for valid reasons such as development of vaccines or other ways to combat emerging pathogens.
But the rules governing its research remain patchy, with no international governance regime in place.
Last year the US government tightened rules on gain of function research. Some experts argue the revised rules, which were weakened from an initial plan that some scientists warned could hobble work on less hazardous pathogens, have troubling gaps.
The focus on federally funded research pays insufficient attention to non-federally financed work and experiments on novel pathogens, said Alina Chan, a viral vector engineer at MIT and Harvard’s Broad Institute.
“The prediction of pandemic risk arising from novel experiments is difficult even for multidisciplinary teams of experts, and a self-reporting system is inadequate as evidenced by past incidents,” Chan wrote in a paper published last month.
US politicians such as Senator Rand Paul have long called for closer scrutiny of gain-of-function research. The debate, like that over Covid’s origins, will remain hotly contested for years to come.
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