WASHINGTON (AP) — President Joe Biden tested positive for COVID-19 on Thursday and is experiencing “very mild symptoms,” the White House said, as new variants of the highly contagious virus are challenging the nation’s efforts to get back to normal after two and a half years of pandemic disruptions.

White House Press Secretary Karine Jean-Pierre said Biden has begun taking Paxlovid, an antiviral drug designed to reduce the severity of the disease. He was isolating at the White House and “continuing to carry out all of his duties fully,” she said.

Biden’s physician, Dr. Kevin O’Connor, said in a letter that Biden had a runny nose and “fatigue, with an occasional dry cough, which started yesterday evening.”

“Folks, I’m doing great. Thanks for your concern,” Biden tweeted. He added that he was “keeping busy!”

Biden, 79, is fully vaccinated, after getting two doses of the Pfizer coronavirus vaccine shortly before taking office, a first booster shot in September and an additional dose March 30.

Jean-Pierre described the president’s symptoms as “very mild” and said Biden had been in contact with members of the White House staff by phone and would participate in his planned meetings “via phone and Zoom from the residence.”

The White House took steps to show that the president was busy working despite his diagnosis, with Biden tweeting out a picture of himself making calls from the treaty room of the White House.

The president spoke by phone to lawmakers in Pennsylvania to apologize for having to cancel his planned trip Thursday to the city of Wilkes-Barre to promote his crime prevention plans. Biden also called South Carolina Rep. Jim Clyburn to wish him a happy birthday and congratulate him on receiving an award from the NAACP.

O’Connor wrote in his letter about the president’s treatment plan: “I anticipate that he will respond favorably” to Paxlovid “as most maximally protected patients do.”

Jean-Pierre said Biden had last tested negative on Tuesday, and he will stay isolated until he tests negative again.

First lady Jill Biden, speaking to reporters as she arrived for a school visit in Detroit, said she’d just gotten off the phone with her husband.

“He’s doing fine,” she said. “He’s feeling good.”

The first lady, who was wearing a mask, said she tested negative earlier in the day. She will keep her full schedule in Michigan and Georgia on Thursday, though she will be following guidance from the Centers for Disease Control and Prevention on masking and distancing, said Michael LaRosa, her spokesperson.

The president spent much of last week in Israel and Saudi Arabia. White House officials told reporters that Biden planned to minimize contact during the trip, yet as soon as he exited Air Force One on July 13, the president was fist-bumping, handshaking and even seen in the occasional hug. The CDC says symptoms can appear two to 14 days after exposure to the virus.

Biden had a minimal public schedule after returning from Saudi Arabia late on Saturday night, attending church the next day and helping to welcome Ukraine’s first lady Olena Zelenska to the White House on Tuesday. The president traveled to Massachusetts on Wednesday to promote efforts to combat climate change.

Dr. Graham Snyder, an infectious disease specialist at the University of Pittsburgh, said in an interview that it wasn’t surprising that Biden tested positive given the extent of his activities and interactions with people. He said Biden appears to be pursuing a treatment that should enable him to recover without facing even worse health risks.

“He’s put himself in a place to have the best possible outcome, which is the lowest probability of being sick enough to get in the hospital or heaven forbid in intensive care or dying,” Snyder said.

Up to this point, Biden’s ability to avoid the virus seemed to defy the odds, even with the testing procedures in place for those expected to be in close contact with him. Prior waves of the virus swept through Washington’s political class, infecting Vice President Kamala Harris, Cabinet members, White House staffers and lawmakers. Biden has increasingly stepped up his travel schedule and resumed holding large indoor events where not everyone is tested.

A White House official said Harris tested negative for COVID-19. She was last with the president on Tuesday and spoke with him on the phone Thursday morning. Harris planned to remain masked on the guidance of the White House medical team.

House Speaker Nancy Pelosi said she hoped that Biden’s positive test for the virus would cause more Americans to get vaccinated and boosted because “none of us is immune from it, including the president of the United States, and we really have to be careful.”

Senate Republican Leader Mitch McConnell on Twitter wished the president “a speedy recovery.”

Top White House officials in recent months have been matter-of-fact about the likelihood of the president getting COVID, a measure of how engrained the virus has become in society — and of its diminished threat for those who are up to date on their vaccinations and with access to treatments.

When administered within five days of symptoms appearing, Paxlovid, produced by drugmaker Pfizer, has been proven to bring about a 90% reduction in hospitalizations and deaths among patients most likely to get severe disease.

Biden is far from the first world leader — and not the first U.S. president — to get the coronavirus, which has infected British Prime Minister Boris Johnson, French President Emmanuel Macron and more than a dozen other leaders and high-ranking officials globally.

When Biden’s predecessor, President Donald Trump, contracted the disease in October 2020, it was a far different time. Vaccines were not available and treatment options were limited and less advanced. After being diagnosed with COVID-19 at the White House, Trump was given an experimental antibody treatment and steroids after his blood oxygen levels fell dangerously low. He was hospitalized at Walter Reed National Military Medical Center for three days

After more than two years and over a million deaths in the U.S., the virus is still killing an average of 353 people a day in the U.S., according to the CDC. The unvaccinated are at far greater risk, more than two times more likely to test positive and nine times more likely to die from the virus than those who have received at least a primary dose of the vaccines, according to the public health agency.

The highly transmissible omicron variant is the dominant strain in the U.S., but scientists say it poses a lower risk for severe illness to those who are up to date on their vaccinations. Omicron’s BA.5 sub-strain, believed to be even more contagious, now makes up more than 65% of U.S. cases.

“There’s a lot of infections across America,” White House COVID-19 coordinator Dr. Ashish Jha said May 18, blaming the highly-transmissible variants, as well as relaxing mitigation measures like mask requirements.

The coronavirus pandemic helped put Biden in the White House, as he pledged to handle COVID-19 better than his predecessor. After initial months of success surging the nation’s supply and availability of vaccines, the virus became a morass for the Democrat in the first year of his presidency, as he struggled to boost the country’s vaccination rate and to stay ahead of the unpredictable disease.

As cases sharply declined earlier this year, Biden highlighted his administration’s efforts to end the pandemic and help the nation regain a sense of normalcy. He said in his March 1 State of the Union address, “It’s time for Americans to get back to work and fill our great downtowns again.”

The White House has sought to go above public health guidelines to protect the president, with all visitors and staff required to attest to their vaccination status or submit to daily tests. People expected to be in close proximity to Biden are tested daily.

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