President Biden tested positive for Covid on Wednesday, according to the White House, forcing him to cancel an event in Las Vegas and likely sidelining him for days following the conclusion of former President Donald J. Trump’s nominating convention on Thursday.
Karine Jean-Pierre, the White House press secretary, said in a statement that “earlier today, following his first event in Las Vegas, President Biden tested positive for COVID-19.” She added that “he is vaccinated and boosted and he is experiencing mild symptoms.”
She said Mr. Biden would travel from Las Vegas to Delaware, where he will “self-isolate and will continue to carry out all of his duties fully during that time. The White House will provide regular updates on the president’s status as he continues to carry out the full duties of the office while in isolation.”
The illness — Mr. Biden’s third bout with Covid, including one rebound case — comes as some of his allies and supporters are continuing to press for him to drop out of the race, citing concerns about his ability to defeat Mr. Trump in November.
Mr. Biden’s doctor, Kevin O’Connor, said in a release from the White House that the president had a runny nose, a cough and “general malaise” starting Wednesday afternoon. Dr. O’Connor said that he was given a rapid test for Covid because he was still not feeling good later in the day, and the results were positive for the virus.
“Given this, the president will be self-isolating in accordance with C.D.C. guidance for symptomatic individuals,” he wrote. He added that the president’s temperature was normal and his blood oxygen was normal as well.
Mr. Biden has received an initial dose of Paxlovid, a treatment that can lessen the symptoms of the virus.
Before announcing the test results, Mr. Biden stopped at a restaurant earlier in the day. Reporters with him said he looked slower and a bit more pale than the day before, when he delivered a speech at the N.A.A.C.P. convention.
Mr. Biden leaned out of his limousine as he arrived at Air Force One to fly back to Delaware and gave reporters a thumbs-up. When they asked how he was feeling, he replied: “Good. I feel good.”