The report, while not a formal scientific document, represents a possible template for a future investigatory hearing in Congress if Republicans gain control of the House or Senate — or both — following the midterm elections. The so-called “lab leak” theory is a talking point for some Republicans seeking office, and Sen. Rand Paul (R-Ky.) has promised hearings if his party wins the Senate.

The 35-page “interim” report released Thursday comes from Sen. Richard Burr (R-N.C.) and Republican staffers on the Senate Health, Education, Labor and Pensions Committee, which has been probing the origin of the virus.

Although the report favors the “lab leak” origin, it does not rule out a market origin. The report also does not indulge the more provocative arguments for how SARS-CoV-2 entered the human population. There is no claim that the virus was engineered as a bioweapon, for example.

Nor does it mention Anthony S. Fauci, the head of the National Institute of Allergy and Infectious Diseases, who has been a frequent target of Paul and other lab-leak proponents because his institute helped fund virus research at the Wuhan Institute of Virology.

For those still trying to duck covid, the isolation is worse than ever

The report’s conclusions diverge sharply from those of two peer-reviewed studies published in the journal Science this summer that presented the case for the Huanan Seafood Market as the epicenter of the outbreak. One study found a geographical bull’s eye on the market among early cases of the disease that came to be called covid-19. The other study presented an analysis of two early strains of the virus suggesting that there were two and maybe many more distinct spillovers of the virus from animals sold at the market.

Scientists favoring the market origin do not know which animals were infected or where they came from. No animals at the market were tested before the market was closed and cleaned.

“Critical corroborating evidence of a natural zoonotic spillover is missing. While the absence of evidence is not itself evidence, the lack of corroborating evidence of a zoonotic spillover or spillovers, three years into the pandemic, is highly problematic,” the new GOP report states.

Michael Worobey, a professor at the University of Arizona who co-authored both studies published in Science, said the new GOP report “gets the science completely wrong.”

“As the saying goes, when you mix science and politics, you get politics,” he said.

Worobey said the hypothesis of some kind of laboratory incident was worth investigating, and he was among the scientists who wrote a letter to Science in May 2021 arguing that all possible origins should be probed. But he said his investigations and those of other scientists point to a market origin.

He said he is willing to testify if the Republicans call hearings.

David Relman, a professor of medicine at Stanford University who was one of the experts interviewed by the committee staff, praised the report as a credible effort to pull together a great deal of information, including on safety issues at Chinese laboratories.

“I think it’s a sober and fair treatment of what is largely a body of circumstantial evidence that makes the case for both hypotheses,” Relman said. “But in particular raises questions about the assumption that a natural spillover must have been the cause.”

Angela Rasmussen, a virologist at the University of Saskatchewan and co-author of one of the Science papers, dismissed the new GOP report as “speculative hand-waving” and views it as a partisan document.

“This is in service of trying to set up something that would be politically advantageous for one party,” she said. “It’s to make it easier to have essentially show trials for people’s adversaries, which has unfortunately come to include scientists.”

The report lands in the final days of an election cycle where multiple Republicans — including Paul, who sits on the health panel — have accused Fauci of hiding information about the virus’s origins.

“We owe it to the Americans who have lost their lives to the virus, their families, and those still struggling with the pandemic’s societal and economic consequences, to continue investigating the coronavirus’s origins,” Sen. Roger Marshall (R-Kan.) said in a statement Thursday, calling on Fauci to “release all texts, emails, communications, and grant records completely and without redactions.”

Burr, who is retiring this year, has taken a more conciliatory approach with Fauci, praising the longtime government scientist’s work at a hearing last month and attempting to focus the report on broader questions of biosafety.

While concluding that a research-related incident is the “most likely” origin of the outbreak, the new report stops well short of a case-closed declaration. Burr’s introductory note is equivocal.

“This conclusion is not intended to be dispositive,” the report’s main text states. “The lack of transparency from government and public health officials in the [People’s Republic of China] with respect to the origins of SARS-CoV-2 prevents reaching a more definitive conclusion. Should additional information be made publicly available, and subject to independent verification, it is possible that these conclusions would be subject to review and reconsideration.”

The panel’s report was steered by Robert Kadlec, an adviser to Burr who served as assistant secretary for preparedness and response at the Department of Health and Human Services during the Trump administration.

Some health officials, including Robert Redfield, the director of the Centers for Disease Control and Prevention during the Trump administration, have reiterated their belief that a lab leak in China is the most likely cause of the pandemic.

“I think you’re going to see the preponderance of the evidence for the origins of covid-19 is that it didn’t come from natural origins. That’s my own view,” Redfield told a House committee investigating the government’s coronavirus response in March.

In a statement on Thursday, the panel’s top Democrat reiterated that a separate probe into the origins of the virus is ongoing.

“[I]n 2021, I announced a bipartisan oversight effort with Sen. Burr into the origins of this virus. The HELP Committee is continuing bipartisan work on this oversight report,” said Sen. Patty Murray (D-Wash.), the Senate health committee’s chair.