Evidence suggests pandemic came from nature, not a lab, panel says

The acrimonious debate over the origins of the COVID-19 pandemic flared up again this week with a report from an expert panel concluding that SARS-CoV-2 likely spread naturally in a zoonotic jump from an animal to humans—without help from a lab.

“Our paper recognizes that there are different possible origins, but the evidence towards zoonosis is overwhelming,” says co-author Danielle Anderson, a virologist at the University of Melbourne. The report, which includes an analysis that found the peer-reviewed literature overwhelmingly supports the zoonotic hypotheses, appeared in the Proceedings of the National Academy of Sciences (PNAS) on 10 October.

The panel’s own history reflects the intensity of the debate. Originally convened as a task force of the Lancet COVID-19 Commission, a wide-reaching effort to derive lessons from the pandemic, it was disbanded by Columbia University economist Jeffrey Sachs, the commission’s chair. Sachs alleged that several members had conflicts of interest that would bias them against the lab-origin hypothesis.

Sachs and other researchers who contend the scientific community has too blithely dismissed the lab-leak possibility aren’t persuaded by the new analysis. The task force’s literature analysis was a good idea, says Jesse Bloom, a virologist at the Fred Hutchinson Cancer Center who has pushed for more investigations of the lab-leak hypothesis. But he says the zoonosis proponents haven’t provided much new data. “What we’ve seen is mostly reanalysis and reinterpretation of existing evidence.”

Sachs adds that the task force report does not “systematically address” the possible research-related origins of the pandemic. And he contends there was a “rush to judgment” by the National Institutes of Health and “a small group of virologists” to dismiss the possible research-related origins of the pandemic. In September, The Lancet published a report from his commission that gave equal weight to both hypotheses.

When Sachs launched the Lancet origin task force in December 2020, he tapped conservation biologist Peter Daszak to lead it. Daszak heads the nonprofit EcoHealth Alliance, which has funded work on bat coronaviruses at the Wuhan Institute of Virology (WIV). Because the first COVID-19 cases were reported in Wuhan, China, some scientists suspect research conducted at WIV led to the spread of SARS-CoV-2. Sachs came to believe Daszak and other task force members who had links to WIV and the EcoHealth Alliance could not assess that possibility fairly and should step down. After fierce infighting over issues including transparency and access to information, Sachs pulled the plug on the task force in September 2021.

But the members continued to meet. “We had a distinguished, diverse group of experts across a whole range of disciplines, and we thought we had something to offer whether or not we were part of the commission,” says Gerald Keusch, an infectious disease specialist at Boston University.

In assembling its report, the task force interviewed researchers who have different perspectives on the pandemic’s origin. It also reviewed the history of RNA viruses, like SARS-CoV-2, that naturally have made zoonotic jumps and triggered outbreaks. And it combed through the scientific literature for papers addressing COVID-19’s origins.

The final product overlaps with the wider ranging Lancet commission report. Both stress the need to address how forces such as growing deforestation and the illicit trade of wild animals increase the risk of viral spillovers. Both emphasize the risk of lax safety measures in labs, as well as in field studies that hunt for pathogens.

But the two reports part ways when it comes to the origin of the pandemic.

The PNAS authors say their literature search revealed “considerable scientific peer-reviewed evidence” that SARS-CoV-2 moved from bats to other wildlife, then to people in the wildlife trade, finally causing an outbreak at the Huanan Seafood Market in Wuhan. In contrast, they say, relatively few peer-reviewed studies back the lab-leak idea, and Daszak notes much of the argument has been advanced through opinion pieces. “The most parsimonious hypothesis is that the pandemic emerged through the animal market system,” Daszak says. “And while the evidence could be a lot better, it’s fairly good.”

He also agrees, however, that the question of how the pandemic began has yet to be answered conclusively. No one has independently audited how viruses were handled at WIV, for example. And no reports exist of scientists testing mammals at animal farms in China that supplied the Huanan market or the humans who handled them. “Absent those two critical pieces of data, you’re left with what’s available,” Daszak says. “What we concluded is that the weight and quality of the evidence is far higher on the natural origins idea.”

The PNAS perspective also stands apart for its recommendations on how to improve warnings that a pandemic is brewing. In a section called “looking forward,” the authors promote “smart surveillance” that would concentrate on transmission hot spots where humans and wild animals frequently come in contact, using cutting-edge technologies to look for novel viruses. Assays now exist that can measure antibodies to an enormous range of viruses, offering evidence of infections that occurred in the past. Wastewater sampling could use new polymerase chain reaction techniques to fish for both known and novel pathogens. And researchers could sample the air on public transport and manure pits on farms.

“For nearly 3 years we’ve been running in circles about different lab-leak scenarios, and nothing has really added to this hypothesis,” says co-author Isabella Eckerle, a virologist at the University of Geneva. “We have missed the chance to say … what can we do better the next time?”

Co-author Linda Saif, a swine coronavirus researcher at Ohio State University, Wooster, says studies of human and animal viral infections remain too siloed and must be combined. “There’s no source of funding for those at this time.”

David Relman, a microbiome specialist at Stanford University who thinks the different origin scenarios are equally plausible, believes the PNAS and Lancet commission reports are “not at all contradictory or inconsistent with each other.” And Relman, who was interviewed by the task force, compliments it for highlighting the need to better prepare for a new pandemic. “At the end of the day,” he says, “this much is true: Spillovers, outbreaks, and pandemics are the result of human activities, for which much greater scrutiny, mindfulness, and insight are desperately needed.”