WASHINGTON - U.S. President Joe Biden was set for a busy day despite ongoing mild COVID-19 symptoms, the White House said on Friday, one day after he tested positive for the virus as a highly contagious subvariant drove a new wave of cases in the United States.

"He was doing just fine," as of Thursday night, said White House COVID Coordinator Dr. Ashish Jha.

"The symptoms were basically the same," Jha said on CNN, adding that he would check the president's condition again on Friday morning. "As of 10 p.m. ... he said he was feeling just fine."

Biden tested positive for COVID-19 on Thursday, when the White House said he was experiencing mild symptoms and would continue working but in isolation.

On Friday, as the White House sought to convey a sense of normalcy, it released another photo of Biden signing legislation a day earlier wearing a black mask.

Biden, who at 79 is the oldest person ever to serve as president of the United States, is due to hold three virtual meetings with his staff on Friday, including his economic, legislative and national security aides, according to his public schedule released by the White House.

"We are going to let him try to get a little bit of a break in there, but I know he wants to have a busy day," Jha said separately on MSNBC. "We'll see what we can negotiate in terms of making sure he gets at least some kind of a break, but he's got a pretty packed day ahead."

Biden began experiencing a runny nose, fatigue and an occasional dry cough late on Wednesday and is taking the antiviral treatment Paxlovid, White House physician Kevin O'Connor said on Thursday.

Fully vaccinated and twice boosted, Biden said he was "doing well" in a video posted on his Twitter account on Thursday. In the 21-second clip, he also said he was "getting a lot of work done" and would continue with his duties.

Jha said it was still unclear where exactly Biden, who recently returned from a trip to the Middle East, contracted the novel coronavirus. He told CNN he was unaware of any linked cases among Biden's recent close contacts but that the White House was continuing to conduct contract tracing.

Jha said he and O'Connor would provide updates of Biden's condition, and the White House has scheduled a news briefing for an update on Biden's health at 3 p.m. EDT (1900 GMT).

U.S. COVID cases have jumped more than 25% in the last month, according to data from the Centers for Disease Control and Prevention (CDC), as the new BA.5 subvariant takes hold there and across the world.

'THE BEST CARE THERE IS'

Biden had been planning to travel to his home state of Delaware this weekend but instead first lady Jill Biden, who has so far tested negative, will stay there while the president isolates in the White House.

U.S. Vice President Kamala Harris has also tested negative.

Paxlovid, the Pfizer Inc antiviral drug the president is taking, has been shown to reduce the risk of severe disease by nearly 90% in high-risk patients if given within the first five days of infection, but has also been associated with rebound infections in some cases.

Even with the powerful antiviral drug and vaccines, a small percentage of older people do wind up in the hospital.

However, health experts have noted that Biden appears to be in relatively good health for his age, echoed by the president's physical in late 2021. He has temporarily stopped taking two medications - one to treat atrial fibrillation, or AFib, and a cholesterol-lowering statin drug - while on Paxlovid.

"He's obviously ... getting the best care there is," Jha told MSNBC.

(Reporting by Susan Heavey and Katharine Jackson; editing by Trevor Hunnicutt, John Stonestreet and Jonathan Oatis)