Trump Leaves Hospital, Minimizing Virus and Urging Americans ‘Not to Let It Dominate Your Life’

But advisers said Mr. Trump wanted to demonstrate from the Oval Office that he was back and healthy, and they were unsure if they could prevent that. Mr. Trump is eager to show that he is a viable candidate for re-election, and advisers said he still planned to go ahead with the second debate with Mr. Biden scheduled for Oct. 15.

While not as equipped as Walter Reed, the White House has a medical unit fully staffed by military doctors and assistants around the clock and capable of providing care to the president. With private examination rooms, a supply of medicine and a crash cart for emergency resuscitation, it has been described by one former White House physician as “like a mini urgent-care center.”

The outbreak in the West Wing continued to spread on Monday as Kayleigh McEnany, the White House press secretary, and two of her assistants tested positive for the virus, heightening fears that more cases were still to come.

Ms. McEnany said she had tested negative several times, “including every day since Thursday,” but health experts said she may have been infectious for days — including when she spoke briefly to reporters without a mask outside the White House on Sunday. Two more members of the press team, Karoline Leavitt and Chad Gilmartin, who is Ms. McEnany’s relative, also tested positive, according to two people familiar with the diagnoses.

The three joined a growing list of people around the president who have tested positive, including Melania Trump, the first lady; Hope Hicks, a senior adviser; Nicholas F. Luna, the director of Oval Office Operations; Bill Stepien, the president’s campaign manager; Ronna McDaniel, the chairwoman of the Republican National Committee; Kellyanne Conway, the president’s former counselor; former Gov. Chris Christie of New Jersey, the president’s debate coach; and at least three White House reporters and two members of the residence staff.

The culture of the White House under Mr. Trump is not to talk about the coronavirus tests. When he received his own initial positive result on a rapid test last Thursday shortly after returning from Bedminster, N.J., he wanted it kept quiet, according to people close to him. Likewise, the two members of the residential staff who tested positive a few weeks ago were advised by colleagues to “use discretion” in discussing it, people familiar with the conversations said.

Vice President Mike Pence, who tested negative on Sunday, was scheduled to travel to Utah ahead of Wednesday night’s vice-presidential debate. Mr. Pence also plans to attend campaign events in Arizona and Florida this week before stopping in his home state, Indiana, to vote early.