Lawmakers who traveled with Biden are still at the Capitol but are testing and masking.

President Biden’s positive coronavirus test on Thursday offered a stark reminder of how the pandemic and the increasing number of variants continue to impede efforts to return to a normal routine in Washington.

“Anything that affects the president has an impact in our country,” Speaker Nancy Pelosi of California said at her weekly news conference on Thursday. She added, “Let’s hope that it would encourage people to be tested, to have the vaccines, the boosters and the rest.”

“None of us is immune from it, including the president of the United States, and we really have to be careful,” Ms. Pelosi said. She has extended proxy voting, a system that has allowed lawmakers to vote remotely since the beginning of the pandemic, through early August.

Lawmakers in both parties were quick to wish Mr. Biden a smooth recovery. Those who had traveled with him to Massachusetts on Wednesday remained on Capitol Hill on Thursday, testing in the morning and confirming plans to continue doing so.

“I’m wearing a mask, I’m getting tested, and I have no symptoms,” said Senator Elizabeth Warren of Massachusetts, one of those lawmakers. Ms. Warren, who tested negative Thursday morning, added: “I will wear a mask because it’s the right thing to do. Democrats continue to test, and when they test positive, they stay home.”

Other lawmakers who traveled with Mr. Biden, including Senator Edward J. Markey of Massachusetts, said they planned to remain masked and socially distanced during the final congressional votes of the week, as well as continuing to test regularly. A spokesman for Representative Jake Auchincloss, another Massachusetts Democrat on the trip, confirmed that the congressman had tested negative Thursday morning and remained asymptomatic.

Any infections, particularly in the Democratic caucuses, could upend Mr. Biden’s agenda. Efforts to move quickly on nominations and legislation have been snarled by absences in the evenly divided Senate in recent weeks, as Senator Chuck Schumer of New York, the majority leader, and other Democrats have announced positive tests this month.

One Democrat, Senator Tina Smith of Minnesota, is currently out after reporting on Wednesday that she had tested positive. Another Democrat, Senator Tom Carper of Delaware, announced on Thursday he had also tested positive, though he had not been on the trip with Mr. Biden. Mr. Schumer is among the senators who have recovered and returned to work.

But it appears unlikely that the Capitol will take any stricter precautions, as crowds of masked and unmasked tourists wander through the hallways and a majority of lawmakers choose to work without a mask.