Dr. Anthony Fauci
Dr. Anthony FauciReuters

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and President Biden's chief medical adviser, tested positive for COVID-19 on Wednesday, the institute said.

Fauci, 81, has mild symptoms and has been boosted twice, the institute said in a statement quoted by CNN. The institute told the network that he is being treated with the antiviral medication Paxlovid.

Fauci was scheduled to testify Thursday at a hearing of the Senate Health, Education, Labor, and Pensions Committee on the status of the federal response to COVID-19 and future plans to manage the pandemic.

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 has not had any close contact with Biden or other senior officials recently, the institute said.

Fauci had previously also advised President Donald Trump on the fight against COVID-19, but the two had a contentious relationship.

Trump reportedly at one point considered demoting the top doctor after he criticized his policies.

In October of 2020, Trump was heard criticizing Fauci in a call with campaign staffers, suggesting he was an "idiot" and saying, "He's been here for, like, 500 years.”

More recently, however, Fauci praised Trump after he said during a speaking tour that he had received a COVID-19 vaccine booster shot.