Embattled WHO virus origins team says window closing for probe

The researchers, writing in the journal Nature, defended their initial efforts and said a second phase is essential to get clear answers about how the pathogen emerged. The planned work includes efforts to find evidence of the virus before it was detected in Wuhan in December 2019, as well as surveys of wildlife that could have harbored the pathogen.

"The window of opportunity for conducting this crucial inquiry is closing fast: any delay will render some of the studies biologically impossible," they wrote, speaking out for the first time after months of controversy. "Understanding the origins of a devastating pandemic is a global priority, grounded in science."

The independent international researchers came in for harsh criticism after they published a joint report with colleagues from China in March laying out a suite of potential paths SARS-CoV-2 could have taken before infecting humans. The most prevalent complaint was that they didn't thoroughly address the potential that it could have leaked from a nearby lab, something they said they acknowledged even though it wasn't part of their original remit.

"We had limited time on the ground in Wuhan and a limited mandate," according to the article authored by 11 of the public health experts who took part in the month-long mission to the city where the virus was first detected. "This initial study was not expected to provide definitive answers to the origin of SARS-CoV-2. Rather, phase 1 was always intended to form the foundation of a longer process of scientific investigation that could last for months or years."

They also addressed other criticisms leveled at the report, denying that they had been pressured by China to include that frozen food was a potential pathway. "Some of the public discourse around the report probably originates from miscommunication and misunderstanding about the nature of the work," they wrote.

The experts reiterated that their view is that the currently available data do not support giving the lab leak theory the same weight as the theory that the virus emerged from an intermediate host.

The furor that met the first report and continuing tensions between the U.S. and China make the chances of continuing WHO-led investigation in China or other countries increasingly faint. Last month, China said it would not put further resources into any probe that included the lab-leak theory, which White House Press Secretary Jen Psaki assailed as "stonewalling" and "irresponsible."

President Joe Biden ordered his intelligence agencies to probe the situation earlier this year. The still-classified investigation didn't come to any firm conclusions on the origins of the virus, according to the Washington Post.

WHO officials said additional studies are already underway, if not by the same group of scientists. The agency has always expected that there would be many missions and long-term collaboration, with different teams working on a variety of topics, said Maria Van Kerkhove, the WHO's technical lead officer on Covid.

"The SARS-CoV-2 work doesn't stop," she said in an interview with Bloomberg on Tuesday. "The report published in March outlined very clearly dozens of studies that need to be carried out immediately," she said. "We understand from our Chinese colleagues that a number of those studies are underway already."

The original group pushed back against having their work be taken over by another committee, such as the one proposed in the wake of the criticism by the WHO called an International Scientific Advisory Group for Origins of Novel Pathogens, or SAGO. While such a committee is essential for routine investigations of outbreaks in the future, relying on it to delve deeper into the cause of Covid-19 would delay the effort by months to disastrous effect, they wrote.

Biological evidence, including antibodies that humans produce during infections, are likely to fade with time, they wrote. Chinese wildlife farms that employed millions of people and supplied live animals to markets in Chinese cities are already closed and their animals dispersed or destroyed, making it hard to find evidence of early spillover to humans.

"Crucially, the window is rapidly closing on the biological feasibility of conducting the critical trace-back of people and animals inside and outside China," they wrote. "We call on the scientific community and country leaders to join forces to expedite the phase 2 studies detailed here, while there is still time."

The WHO's Van Kerkhove said the SAGO committee would build off the earlier work, and fold in other recent publications on topics ranging from animal susceptibility to surveys of viruses in bat species and wastewater.

The Nature article was signed by all but one member of the team, which is comprised of people from various nations and scientific fields including several who received death threats following the publication of the report. The one member who did not sign was Peter Ben Embarek, a food-safety scientist at the WHO in Geneva who led the effort. He declined to comment.