CNN interrupted Tuesday's Senate Health Committee hearing with Dr. Anthony Fauci and other health officials to try and fact-check Sen. Rand Paul, R-Ky., concluding he was "mercilessly attacking" the witness sans evidence.

Paul pressed Fauci on reports that the U.S. funded the Wuhan Insitute of Virology for gain-of-function research, alleging that a U.S. virologist had been working with the Chinese institute and the work was bankrolled by the National Institute of Health. Some experts have alleged that the COVID-19 virus escaped following experimentation in the Wuhan lab.

"Senator Paul, with all due respect, you are entirely, entirely and completely incorrect," Fauci responded. "The NIH has not ever and does not now fund gain-of-function research in the Wuhan Institute of Virology."

While the NIH has fundied Chinese research, Fauci said Paul was unfairly conflating that fact with the risky research in Wuhan. Former Centers for Disease Control and Prevention (CDC) Director Robert Redfield told CNN last month that he believed the coronavirus escaped from the Wuhan lab.

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CNN, shortly after one of its anchors called Paul an "a--" for his prior criticisms of Fauci, cut in to the hearing and quickly took the side of the infectious disease expert.

CNN congressional correspondent Lauren Fox said Fauci seemed "prepared" and "calm" throughout the exchange, while anchor Kate Bolduan and her guests seemed confused by Paul's line of questioning.

"It is unclear I think to everyone who is watching what tangent just happened with Rand Paul and why he was so mercilessly attacking Dr. Fauci," CNN anchor Kate Bolduan said.

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Bolduan asked for an explanation from Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, and he joined in on the excoriation of Paul.

"Sen. Paul has had it in for Tony, for Dr. Fauci for this whole COVID-19 pandemic," Hotez said. "And he likes to spar with Dr. Fauci at these Senate hearings, always brings up weird herd immunity numbers and that sort of thing. Look, the evidence that COVID-19 originated from the Wuhan lab is very weak. And my point has always been, we don’t have to postulate that."

Republicans disagree. In a letter to Secretary of State Antony Blinken, Rep. Cathy McMorris Rodgers, R-Wash., led a group of lawmakers demanding answers to the "lab leak" theory.

In the letter, they request "unclassified documents and declassify other documents for public release, as appropriate, related to the assertion in the Department’s January 15, 2021 Fact Sheet that the Wuhan Institute of Virology (WIV) in Wuhan, China, collaborated with the Chinese military in conducting classified research, including laboratory animal experiments."

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CNN political analyst David Chalian argued Paul merely wanted to get a fundraising boost out of his argument with Fauci. The segment was accompanied by the chyron: "Fauci, GOP Sen. Rand Paul Spar Again Over Senator's Misleading Info."