Fauci, the director of the National Institute of Allergy and Infectious Diseases and a leading member of the task force, has become nationally known for his simple and direct explanations to the public about the coronavirus and COVID-19, the disease it causes.

Also quarantining are Dr. Robert Redfield, director of the Centers for Disease Control and Prevention, and the commissioner of the Food and Drug Administration, Stephen Hahn.

Fauci's institute said that he has tested negative for COVID-19 and will continue to be tested regularly. It added that he is considered at “relatively low risk” based on the degree of his exposure, and that he would be “taking appropriate precautions" to mitigate the risk to personal contacts while still carrying out his duties. While he will stay at home and telework, Fauci will go to the White House if called and take every precaution, the institute said.

Redfield will be “teleworking for the next two weeks" after it was determined he had a “low risk exposure" to a person at the White House, the CDC said in a statement Saturday evening. The statement said he felt fine and has no symptoms.

Just a few hours earlier, the Food and Drug Administration confirmed that Hahn had come in contact with someone who tested positive and was in self-quarantine for the next two weeks. He tested negative for the virus.

All three men are scheduled to testify before a Senate committee on Tuesday. Sen. Lamar Alexander, R-Tenn., the chairman of the panel, said the White House will allow Redfield and Hahn to testify by videoconference, a one-time exception to the administration's policies on hearing testimony. The statement was issued before Fauci's quarantine was announced.

Vice President Mike Pence's press secretary tested positive for the coronavirus on Friday, making her the second person who works at the White House complex known to test positive for the virus this week. White House officials had confirmed Thursday that a member of the military serving as one of Trump’s valets had tested positive for COVID-19 on Wednesday.

President Donald Trump, who publicly identified the affected Pence aide as spokeswoman Katie Miller, said he was “not worried” about the virus spreading in the White House. Nonetheless, officials said they were stepping up safety protocols for the complex.

Miller had been in recent contact with Pence but not with the president and had tested negative a day earlier. She is married to Stephen Miller, a top Trump adviser. The White House had no immediate comment on whether Stephen Miller had been tested or if he was still working in the White House.

The CDC and FDA would not disclose the identity of the person who had tested positive and with whom the agency leaders had come in contact.

Trump has resisted wearing a mask, and in a meeting with the nation’s top military leaders Saturday evening, he did not wear a mask during the brief portion that reporters were allowed to view. The generals around Trump also did not wear a mask, but participants did sit a few feet away from each other.

White House chief of staff Mark Meadows said the administration was stepping up mitigation efforts already recommended by public health experts and taking other unspecified precautions to ensure the safety of the president. He said the White House was “probably the safest place that you can come,” but the he was reviewing further steps to keep Trump and Pence safe.