As the leader of the host nation, Mr. Sen had contact with almost all the top-level participants. During the session, almost none of the leaders or other participants wore masks, and everyone sat close to each other, often for long periods of time. But White House officials played down suggestions that Biden may have the virus for a third time, after he was infected in July and then suffered a rebound two days after testing negative. Biden was negative Tuesday morning, they insisted. “It’s not Covid. He just had a full day in meetings and had to attend to a few things tonight (nothing urgent!),” an official said when asked by reporters why he was skipping the gala dinner. “He spoke to Widodo (Indonesian President Joko Widodo) to express his regret at missing the dinner and Widodo said it was not an issue and P (Joe Biden) is looking forward to seeing him at the mangrove tomorrow.”