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Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, listens during a Senate Health, Education, Labor and Pensions Committee hearing on June 30, 2020 in Washington, DC.

 (CNN) — Dr. Anthony Fauci hit back at two Republican senators in a pair of tense exchanges Tuesday, accusing one of attacking him for political gain and calling another "a moron" following questions about his finances during a Senate hearing.

The confrontations with Sens. Rand Paul and Roger Marshall came in a hearing on the federal response to the omicron variant of COVID-19 as the Biden administration faces growing scrutiny alongside record hospitalizationstesting challenges and messaging frustration — issues the GOP has seized on.

Early in the hearing, after Paul sought to cast Fauci as a "dangerous" government official, the White House chief medical adviser and top infectious disease expert said such rhetoric "kindles the crazies" and has led to threats against his family.

"What happens when he gets out and accuses me of things that are completely untrue is that all of a sudden that kindles the crazies out there and I have life — threats upon my life — harassment of my family, and my children, with obscene phone calls because people are lying about me," Fauci said before suggesting the Kentucky Republican was attacking him as a way of raising money.

"So I asked myself, 'Why would Senator want to do this?' So, go to Rand Paul website. And you see, 'Fire Dr. Fauci' with a little box that says, 'contribute here,' you can do $5, $10, $20, $100," he said. "So you are making a catastrophic epidemic for your political gain."

Fauci brought a similarly pointed tone to his exchange with Marshall after the Kansas Republican falsely accused him of withholding financial disclosure forms.

"You're so misinformed, it's extraordinary," a visibly frustrated Fauci told Marshall, calling his financial information "public knowledge" for nearly four decades. After the back-and-forth, Fauci could be heard saying, "What a moron. Jesus Christ."

Speaking with CNN's Anderson Cooper on "AC360" Tuesday evening, Fauci said public health officials "should be having to respond to tough questions."

"And yet, the only thing that came out of Sen. Rand Paul and, to some extent, Sen. Roger Marshall, were ad hominems, which does nothing but distract from what we really need to be doing," he said.

In response to the hearing, a spokesman for the Department of Health and Human Services told CNN in a statement Tuesday that Republicans on the panel "clearly weren't trying to stop the spread" of misinformation.

"At a time when America is seeing rising COVID cases, it's disappointing and frankly unacceptable that Republican Senators chose to spend a hearing with the country's leading public health experts spreading conspiracy theories and lies about Dr. Fauci, rather than how we protect people from COVID-19," spokesman Ian Sams said.

"The Biden Administration will continue to focus on getting more Americans vaccinated and boosted and helping Americans get access to the tools to keep themselves and others safe. We would encourage these Republicans to join us."

The United States averaged more than 754,200 new COVID-19 cases daily over the past week, according to Johns Hopkins University data. That's about three times last winter's peak average (251,987 on January 11, 2021), and 4.5 times the peak from the Delta-driven surge (166,347 on September 1), according to Johns Hopkins.

"Omicron, with its extraordinary, unprecedented degree of efficiency of transmissibility, will ultimately find just about everybody," Fauci told J. Stephen Morrison, senior vice president of the Center for Strategic and International Studies, on Tuesday.

"Those who have been vaccinated ... and boosted would get exposed. Some, maybe a lot of them, will get infected but will very likely, with some exceptions, do reasonably well in the sense of not having hospitalization and death."