Wednesday, May 12, 2021

in-focus

WHO report leaves unsettled 'lab-leak' theory on origins of covid pandemic


Shortly after evidence emerged that a new coronavirus was spreading in the Chinese city of Wuhan in January 2020, speculation mounted about the origins of the lethal pathogen.

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Right-wing news outlets in the United States published tendentious and thinly sourced reports that the virus may have come from the Wuhan Institute of Virology, famous in the scientific community for researching coronaviruses in bats. In April, President Donald Trump suspended U.S. funding for the World Health Organization, which he accused of being subservient to Chinese officials, and said that the U.S. government was investigating the lab as a potential source of the virus.

"A lot of people are looking at it - it seems to make sense," he said.

Since then, more information has accumulated that the virus may have first infected humans after moving through animals, and the "lab-leak theory" usually has been framed as a political distraction, promulgated by a president deflecting attention from his administration's response to the pandemic, and not as a serious scientific question.

No consensus has emerged on where the virus originated, and there are far more scientists who think it developed naturally than who entertain the possibility that it came from a lab.

That made it all the more surprising when, on Tuesday, the head of the WHO said that his agency hadn't sufficiently examined the lab scenario.

"Although the [WHO] 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," Director General Tedros Adhanom Ghebreyesus said at a news conference marking the release of a highly-anticipated report on the virus's origins, which concluded that the virus probably jumped from an infected animal into a human.

Tedros voiced frustration with the level of access Chinese authorities gave the WHO, an unusually public rebuke from an agency that has been mostly solicitous to Beijing.

In recent interviews, some members of the WHO team that flew to Wuhan to gather information have acknowledged that they lacked the expertise, resources or mandate to determine whether the virus may have emanated from a lab.

The lab-leak theory is far from proved, but Tedros's openness was applauded by those who have argued that some circumstantial evidence points to the Wuhan lab as a possible source.

"Making these assertions despite the incredible pressure being placed on him and the WHO represented a bold defense of the organization's integrity in the face of Chinese government efforts to manipulate and restrict the covid-19 origins examination process," said Jamie Metzl, a National Security Council staffer in the Clinton administration and a member of a WHO expert advisory panel, who had helped organize an open letter calling for more scrutiny of the Wuhan lab, unrestricted by Chinese authorities.

Officially, the Biden administration is open to the possibility of a lab leak. A State Department document, published five days before Trump left office, and which has not been retracted, alleged that "several researchers" at the lab became sick in the fall of 2019 with covid-like symptoms, before the first identified case of the disease, and claimed that the lab "has engaged in classified research, including laboratory animal experiments, on behalf of the Chinese military since at least 2017."

Versions of the lab-leak theory imagine that an infected worker may have unknowingly passed the virus to others in Wuhan or that an infected animal may have escaped or been sold.

Lab officials have said they possessed no samples of the virus, SARS-Cov-2. And Shi Zhengli, a renowned coronavirus researcher at the lab, has said none of the staff were infected and that the Chinese military has no connection to the institute.

The WHO report states there was no direct infection of workers but does not go into detail or recommend further research on this or other topics.

From the outset, the WHO investigation was unlikely to unearth much evidence that the virus emanated from a lab.

When a joint international-Chinese team convened in Wuhan in the final days of the Trump administration, their itinerary was focused on exploring possible paths of transmission between human and animals - and even a theory pushed primarily by the Chinese government about transmission via frozen seafood - rather than the lab hypothesis.

The group visited the Wuhan Institute of Virology for a few hours, hearing about the lab's research and safety record and getting assurances that scientists there were not working with viruses closely related to SARS-CoV-2, according to interviews with three foreign scientists on the team and a summary included in the annexes of the WHO's report.

At a post-trip news conference, Peter Ben Embarek, a Danish food safety expert serving as the WHO lead, described the conversation with staff at the lab as "long, frank and open," and he appeared satisfied with the short visit and Chinese assurances.

"They're the best ones to dismiss the claims and provide answers to all the questions," he said, surprising some experts and U.S. officials, who were reluctant to take the staff's word at face value.

The international team's level of interest in exploring the lab theory seemed low, either because they saw it as a politically motivated hoax, thought the evidence pointed in other directions, or did not believe the team had a mandate - or the appropriate staffing - to investigate a Chinese lab.

Dominic Dwyer, an Australian microbiologist and infectious-disease expert on the mission, said he didn't think the possibility of a lab accident could be ruled out but stressed that the team wasn't equipped to investigate the hypothesis.

"So, I mean, yes, we did a three-hour visit, and it was sort of managed in the sense that there's a lot of people there and we did a tour," he said. "But we did get to ask questions and so on."

Hung Nguyen-Viet, a Vietnamese expert on livestock and human health on the team described the institute as a "nice lab and well organized" and the discussions with Chinese scientists there as spirited but collaborative.

Hung emphasized that the team agreed that a lab leak was the least likely path of the virus and therefore put their time and energy into exploring other hypotheses."You would need another team and set of people who really have expertise" to investigate the hypothesis further, he said.

The WHO report also addressed suspicions that the Wuhan institute may have been experimenting with a virus related to SARS-Cov-2 before the outbreak, which in turn might have set the stage for an accidental release.

At a mine in Mojiang, in China's southern Yunnan province in 2013, scientists discovered the closest known relative to the coronavirus, called Ratg13. It shares 96% of its genetic identity with SARS-Cov-2.

That's hardly close enough to mean that Ratg13 itself could have sparked the pandemic. That 4% gap would take decades of evolutionary time to bridge.

Still, Ratg13 may be an important clue to the coronavirus's origins. Yet oddly to some observers, when lab staffers first showed how closely Ratg13 is related to the novel coronavirus, in an article in the journal Nature in early 2020, they did not highlight that it came from the mine. Nor did they note that in 2012, several mine workers who had been tasked with cleaning bat feces there were sickened with a respiratory illness that some have since argued resembles covid-19. Three died.

The Wuhan institute scientists later acknowledged that the cases of the sickened miners initially drew them to conduct extensive research, since they "suspected that the patients had been infected by an unknown virus."

The new WHO report, however, says institute staffers told investigators the miners' illnesses "were more likely explained by fungal infections acquired when removing a thick layer of guano," or bat feces.

The report does not elaborate on that suggestion, which is mentioned briefly in one of the report's annexes under a category titled "Conspiracy Theories."

Meanwhile, there is a larger body of evidence that SARS-CoV-2 emerged in nature.

"My view is: This is another example of a bat virus jumping into humans, either directly or through an intermediate host," said Tony Schountz, an expert in bat-borne viruses at Colorado State University.

When asked whether a lab accident may have been responsible for the Wuhan outbreak, Schountz said it was possible "but, you know, tomorrow I could win the lottery."

Other virus specialists described WHO's exploration as sufficient. "I'm not particularly disappointed that they didn't dig deeper into the Wuhan Institute of Virology," said Joel Wertheim, an associate professor of medicine at University of California at San Diego. "I don't think that idea merited as much investigation as looking for the earliest cases."

Wertheim and his colleagues, in a paper published recently in the journal Science, suggested that the first case of covid-19 may have emerged as late as mid-October to mid-November 2019, before a large cluster of cases linked to a seafood market in Wuhan.

In their models, Wertheim and his co-authors also found coronavirus outbreaks were much more likely than not to fizzle out, especially in rural communities with fewer connections between people. "It's not fair to characterize this virus as sort of the perfect vessel for human-to-human transmission," he said. The pathogen seemed to need a denser, urban area to become a pandemic.

"Even if you believe this came through the lab, what you'd have to then show is that the lab had a virus that was very close to SARS-CoV-2. They haven't found that," said David Robertson, head of viral genomics and bioinformatics at the University of Glasgow. If laboratory scientists "did have it, I don't think they would have hidden it. It wouldn't have occurred to them."

Published : March 31, 2021

By : The Washington Post · Shane Harris, Emily Rauhala, Ben Guarino, Chris Mooney