President Biden in May 2021 asked intelligence agencies to probe the origins of the virus, but they were unable to reach a consensus. Most favored, with “low confidence,” the natural spillover theory. Peer-reviewed scientific papers published last year bolstered the case that the virus came from animals sold at the Huanan Seafood Wholesale Market in Wuhan.

But critics of the natural spillover theory point out that investigators did not find any virus-infected animals that could have been the source of the outbreak. That fact was highlighted in a report issued last year by Republican staff on a Senate committee looking into the origin of the virus. The report also raised questions about safety protocols at a Wuhan laboratory. While not ruling out a natural spillover, the Republican staffers concluded that a “research-related incident” was the “most likely” origin.