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

Biden's symptoms - which include sore throat, runny nose, cough and body aches - remain mild, his physician Kevin O'Connor wrote in a letter released Saturday morning. The president has been taking the antiviral Paxlovid for two 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.

"His pulse, blood pressure, respiratory rate and temperature remain entirely normal," O'Connor wrote. "His lungs remain clear."

Biden, 79, 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.

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. 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 covid tracker.

Biden, who is vaccinated and has received two boosters, continues to isolate in accordance with Centers for Disease Control and Prevention guidelines, the White House said.

The president has continued to work while sick, meeting virtually with his economic team and speaking with staffers on FaceTime on Friday. The White House previously said that Biden will isolate for at least five days and will remain in isolation until he tests negative.

"He is still putting in eight-plus hours of work a day," White House press secretary Karine Jean-Pierre said in a Friday briefing. "Look, the president hopes the country will see that while we should continue to take COVID very seriously, we have the tools we need to deal with this."