Fauci, 81, has mild symptoms and has been boosted twice, the institute said in a statement. The institute told CNN that he is being treated with the antiviral medication Paxlovid.
NIAID said Fauci found out that he was positive on a rapid antigen test. The director will work from home and follow agency protocol, returning to the National Institutes of Health campus only after he tests negative.
Fauci was scheduled to speak Thursday at a hearing of the Senate Health, Education, Labor, and Pensions Committee on the status of the federal response to Covid-19 and plans to manage the pandemic. The agency said he will attend by videoconference.
Fauci has not had any close contact with Biden or other senior officials recently, the institute said.
Throughout the pandemic, he has urged caution and has demonstrated it himself at public events. For instance, he chose not to attend the annual White House Correspondents’ Dinner in April after considering his individual risk.
“Each of us, in our own personal way, has to make an assessment of what risk you’re willing to accept about getting infected,” he told CNN. “In general, the risk is low, but I made a personal assessment. I’m 81 years old, and if I get infected, I have a much higher risk.”
He has been the director of NIAID since 1984 and has advised seven Presidents.
Fauci joins a growing list of Biden administration leaders who have had Covid-19, including White House domestic policy adviser Susan Rice, Attorney General Merrick Garland, Vice President Kamala Harris and Commerce Secretary Gina Raimondo.