Fauci testifying to Senate panel after Rand Paul releases trove of diary entries

The precise origins of the virus that caused the COVID-19 pandemic have not been definitively nailed down — drawing years of debate among politicians, medical experts and intelligence officials.

Many scientists believe the evidence suggests that the virus emerged naturally in bats, circulated to other species and spilled over to humans at a live animal market in Wuhan, China, where the first human cases appeared in late 2019. Others believe the virus accidentally leaked from a laboratory in Wuhan that was carrying out virology research.

Last year, a panel of experts assembled by the World Health Organization was unable to reach a firm conclusion on how the coronavirus emerged. They wrote that the "weight of available evidence" suggested it jumped naturally from animals to humans, but they couldn't rule out a lab leak, in part because China didn't make records available.

The U.S. intelligence community offered a similarly mixed view in 2023. The National Intelligence Council and four other agencies found the virus likely infected humans through natural exposure to an animal, while the FBI and Department of Energy believed it was likely a lab incident. The CIA was unable to reach a conclusion at the time, though it issued a new assessment favoring the lab leak last year.

Some of the debate revolves around "gain-of-function" research, a controversial practice broadly defined as modifying or enhancing viruses to study how they evolve. Paul and other critics have accused the U.S. National Institutes of Health of funding such research at the Wuhan Institute of Virology, and have argued that it may have led to the coronavirus' creation.

During the Biden era, the NIH denied that the bat virus research conducted in Wuhan constituted risky gain-of-function research, and the specific viruses that were studied were "genetically far distant" from the one that caused the pandemic.

Wednesday's hearing could be the latest in a series of explosive confrontations between Fauci and Paul, two medical doctors by training who have publicly accused each other of lying.

Paul has backed the theory that the coronavirus emerged from a lab, and has accused Fauci and other top officials of publicly downplaying and denigrating that theory, especially in the early days of the pandemic. Fauci insists he has always kept an open mind about the virus' origins, though he has argued at various points that the evidence suggests the virus emerged naturally.

Also at issue: "gain-of-function" research. Paul has accused Fauci of lying to Congress by denying that the NIH funded that type