Speaker Nancy Pelosi of California tested positive for the coronavirus, her office said on Thursday, the latest high-profile official to do so as the virus spreads through Washington.

Drew Hammill, a spokesman for Ms. Pelosi, said she was asymptomatic, and had previously been vaccinated and boosted. He added that Ms. Pelosi, 82, had tested negative earlier this week.

“The speaker is fully vaccinated and boosted, and is thankful for the robust protection the vaccine has provided,” Mr. Hammill said, adding that she would isolate consistent with guidance from the Centers for Disease Control and Prevention.

The speaker “encourages everyone to get vaccinated, boosted and test regularly,” he said.

Ms. Pelosi, who is second in the line of succession to the presidency after Vice President Kamala Harris, was among the lawmakers who appeared maskless with President Biden at a bill-signing ceremony at the White House earlier this week.

The positive test came just before her weekly news conference, which was subsequently canceled. Mr. Hammill said that a planned congressional delegation to Asia, which Ms. Pelosi had been scheduled to lead, would be postponed.