WASHINGTON – President Joe Biden, who tested positive for the coronavirus on Thursday, probably has the BA.5 variant and continues to experience mild symptoms that are improving, the White House said Sunday.

His physician, Kevin O’Connor, wrote in a letter that the president’s pulse, blood pressure, respiratory rate and temperature all remain normal, and he doesn’t have any shortness of breath.

“His predominant symptom now is sore throat,” O’Connor wrote, adding that it was an indication that his body is clearing the virus, which is “encouraging.”

The president has taken the antiviral Paxlovid for three days and will continue treatment, O’Connor said. He is also taking Tylenol and using an albuterol inhaler a few times a day for cough.

“The President is responding to therapy as expected,” O’Connor wrote in his latest letter. “The BA5 variant is particularly transmissible and he will continue to isolate in accordance with Centers for Disease Control and Prevention (CDC) recommendations.”

The White House said last week that it would go beyond CDC guidance and ensure that Biden remained in isolation until he tested negative. That goes beyond the CDC’s guidelines from December, which cut its recommended isolation time to five days if a patient’s symptoms were gone or were resolving and then said to wear masks for an additional five days. Some public health experts have criticized the revised CDC guidelines as insufficient, warning that many people who contract the coronavirus remain infectious after the first five days.

Biden, 79, who has been vaccinated and received two boosters, is the second U.S. president to test positive for the coronavirus.

His symptoms have so far been much milder than they were for President Donald Trump, who spent three days at Walter Reed National Military Medical Center in October 2020 after he contracted the virus before the first vaccinations were rolled out.

Ashish Jha, the White House COVID-19 response coordinator, said that the president has had 17 close contacts, including with members of Congress and the White House staff. All were being tracked by the White House medical unit, he added.

“None of them have tested positive as of late yesterday,” Jha said on ABC’s “This Week” on Sunday. “They are following CDC protocol, and we’ll continue to follow them.”

Asked if masking and distancing protocols were being rethought, Jha said that CDC guidelines were being adhered to.

“Protocols around the president I think have been very tight, but this is a president who likes to get out there, meet Americans, spend time with people,” he said.

In recent months, Biden has stressed that Americans who are fully vaccinated can begin resuming their normal routines.

“Thanks to the progress we’ve made in the last year, COVID-19 no longer need control our lives,” he said during his State of the Union address in March.

But new strains – including the highly transmissible BA.5 omicron subvariant, which is responsible for up to 80% of current infections in the United States – have continued to infect millions of Americans, although hospitalization and death rates are significantly lower than they were in the winter, when infections were also soaring. The virus is responsible for 125,000 new cases and more than 400 deaths each day, according to seven-day averages on the Washington Post’s coronavirus tracker.

Biden has continued to work while sick, meeting virtually with his economic team and speaking with staffers on FaceTime on Friday.

Journalists, including several television hosts on Sunday morning, have pressed the White House about why O’Connor, the president’s personal physician, has not directly briefed reporters about Biden’s infection.

“Dr. O’Connor and I are speaking multiple times a day,” Jha said Sunday. Jha said O’Connor is also speaking with Anthony Fauci, Biden’s chief medical adviser. He added: “We are being very transparent, probably giving updates several times a day about how the president is doing.”