The president, who is 79, has started taking Paxlovid, an antiviral treatment made by Pfizer, White House press secretary Karin Jean-Pierre said in a statement announcing his diagnosis. The positive test is the first time Mr. Biden is known to have contracted the coronavirus. “In accordance with CDC guidelines, he will self-isolate at the White House and continue to fully perform all of his duties during this time,” he said. “He was on the phone with members of the White House staff this morning and will participate in his scheduled White House meetings this morning via phone and Zoom from the residence.” In a video message on Twitter, Mr. Biden updated his status, saying he continued to work from the White House residence. “Hey guys, I guess you heard – this morning I tested positive for COVID. But I’ve been double-vaccinated and double-boosted. The symptoms are mild,” the president said. “And I really appreciate your questions and concerns. But I’m doing well, I’m doing a lot of work, I’ll keep getting it done. And in the meantime, thanks for your concern and keep the faith. It’s going to be OK.” An update from me: pic.twitter.com/L2oCR0uUTu — President Biden (@POTUS) July 21, 2022 Mr. Biden’s antigen test first detected the coronavirus and the result was confirmed by a PCR test, White House physician Dr. Kevin O’Connor said in a letter released by the White House. He feels runny, occasionally dry cough and tired. The president is fully vaccinated — he received his first Pfizer shot in December 2020 and his second in January 2021 — and has received two booster shots, most recently in late March. O’Connor wrote that he expects the president “to respond positively, as most maximally protected patients do” to the treatment. In a press conference with Jean-Pierre in the afternoon, Dr. Ashish Jha, the White House’s COVID-19 response coordinator, said the president’s “risk of serious illness is dramatically lower” because he is fully vaccinated and receiving treatment with Paxlovid. “It’s a reminder of why we’re all working so hard to make sure every American has the same level of protection as the president,” Tza told reporters. Before Thursday’s test, Mr. Biden had recently been tested for COVID-19 on Tuesday and the result was negative, Jean-Pierre said. First Lady Dr. Jill Biden tested negative for COVID-19 Thursday morning in Delaware, according to her spokesman Michael LaRosa. The first lady also confirmed her negative test to reporters Thursday in Detroit. “I just talked to him a few minutes ago,” the first lady said of her husband. “He’s doing well, he’s feeling good.” Mr. Biden will continue to “work in isolation until a negative test comes out,” Jean-Pierre said, after which he will return to personal work. The White House will provide daily updates on the president’s condition “out of an abundance of transparency,” he continued. In a message to White House aides obtained by CBS News, chief of staff Ron Klain wrote: “We have said for some time that there was a significant possibility that the President — as well as anyone else — could contract COVID, and we have prepared for this. We are now executing our plan so that the President can continue to work seamlessly from the Residence.” The president was scheduled to travel to Pennsylvania on Thursday, first to Wilkes-Barre for remarks unveiling a crime prevention plan and then to Philadelphia for a fundraising reception for the Democratic National Committee. This trip will no longer take place and will remain at the White House. Vice President Kamala Harris, who had the virus earlier this year, is currently in North Carolina and will wear a mask on the advice of the White House medical team, according to a White House official. She tested negative for COVID-19 on Thursday morning and was last with Mr. Biden on Tuesday, he said. The president and vice president also spoke by phone Thursday. The diagnosis comes days after the president returned from a four-day trip to the Middle East, his first as president, and the day after he delivered remarks in Massachusetts about the actions his administration is taking to combat climate change. Mr. Biden was joined on the trip on Air Force One by members of the Massachusetts congressional delegation, including Massachusetts senators Elizabeth Warren and Ed Markey, both Democrats. Warren tested negative Thursday, her spokesman said, as did Rep. Jake Outchincloss, who also traveled with the president, his communications director tweeted. The White House Medical Unit will inform all of Mr. Biden’s close contacts of his positive test, Jean-Pierre said, including those who interacted with the president during his trip on Wednesday. The president interacted with several politicians on Wednesday when he visited Somerset, Massachusetts. The president has managed to avoid contracting COVID-19 since the start of the pandemic, even as several members of his administration and top lawmakers — some after being close to the president — were diagnosed. Harris tested positive for COVID-19 in April. House Speaker Nancy Pelosi contracted the virus earlier that month after attending two White House events, sharing the stage with Mr. Biden at one. Other members of the president’s cabinet, including Attorney General Merrick Garland, Health and Human Services Secretary Xavier Becerra (who tested positive twice), and Commerce Secretary Gina Raimondo also had COVID-19. The president received well wishes from both Democrats and Republicans, as well as other world leaders, after his diagnosis was revealed. “Saddened to hear that President Biden has tested positive for COVID-19,” Senate Minority Leader Mitch McConnell tweeted. “I wish him a speedy recovery.” British Prime Minister Boris Johnson and Indian Prime Minister Narendra Modi expressed their best wishes to Mr. Biden and hope for a speedy recovery. Fueled by the BA.5 sub-variant, the number of new COVID-19 cases is slowly starting to rise and infections are increasing in many states. Hospitalizations from the coronavirus among Americans age 70 and older have also hit their worst levels since February, according to the Centers for Disease Control and Prevention. In Washington, the community level of COVID-19 is “moderate,” according to the agency, and the White House continued to urge Americans to wear masks indoors in public spaces. Dr. Scott Gottlieb, former commissioner of the Food and Drug Administration, told “Face the Nation” on Sunday that the BA.5 strain has the ability to evade immunity acquired through vaccination and prior infection, and the predicted cases are not reported. “I think most Americans have come to accept this as part of the fabric of everyday life,” he said. Nancy Cordes, Alex Tin and Jack Turman contributed to this report.