Less than a week after his vigorous launch into the New York City mayor’s race, Andrew Yang said on Tuesday that he was halting in-person events and quarantining because a campaign staff member had tested positive for the coronavirus.

Mr. Yang, the former presidential candidate, had been seemingly everywhere in recent days, meeting with elected officials across the city and riding the subway and bus to campaign events. His whirlwind appearances have been in sharp contrast to the mostly virtual campaigns that his rivals have been conducting.

Mr. Yang will enter quarantine for at least eight days, his campaign said in a statement.

“This morning, we learned that a member of the campaign staff received a positive result on a rapid Covid test,” the statement said. “Since that time, Andrew has tested negative and is not experiencing any symptoms.”

The news is likely to raise questions about Mr. Yang’s decision to hold so many in-person events during a second wave of coronavirus cases in New York City. It will also force him off the campaign trail at a time when he had been grabbing attention for his frenetic schedule of public appearances and interviews with journalists.

On Monday, Mr. Yang attended an event at the Rev. Al Sharpton’s headquarters in Harlem to commemorate Martin Luther King Jr.’s Birthday. He spoke without a mask before a large crowd that included many of the other mayoral candidates.

At least two of those candidates have had to quarantine recently: Scott Stringer, the city comptroller, and Maya Wiley, a former counsel to Mayor Bill de Blasio. Eric Adams, the Brooklyn borough president, has separately received criticism for holding in-person fund-raisers.

The staff member who tested positive was with Mr. Yang for most his four-borough campaign kickoff on Thursday, a tour that drew many onlookers as well as a pack of reporters. After announcing his campaign at Morningside Park in Manhattan, Mr. Yang attended a food distribution event in the Bronx; had lunch in Queens with Donovan Richards, the Queens borough president; and did a walking tour of the Brownsville neighborhood in Brooklyn. Mr. Yang did not visit Staten Island.

Chris Coffey, a spokesman for Mr. Yang, said the campaign planned to restart its events after the quarantine period.

“We plan to keep up safe, in-person, outdoor campaigning,” he said. The staff member who tested positive was not at Mr. Sharpton’s event on Monday.

Jon Paul Lupo, an adviser to Ms. Wiley, alluded to the health risks of Mr. Yang’s in-person campaigning.

“Very much looking forward to folks who lauded Yang for in-person events (without mention of health risk) to now laud other campaigns that displayed more caution,” he wrote on Twitter.

Mr. Coffey fired back on Twitter, noting that Mr. Yang was not the only candidate attending in-person events.

“Was great to see Maya Wiley inside” at Mr. Sharpton’s event, Mr. Coffey said. “Didn’t you guys just isolate for 2 weeks?”

Ms. Wiley took a softer tone. “Thinking of you and your family,” she wrote on Twitter to Mr. Yang. “We’ve been there. Stay strong.”

Mr. Yang’s campaign said that he would conduct all activities remotely during his quarantine, and that it had started contact tracing to notify anyone who might have had contact with the staff member. The campaign requires staff members attending in-person events to get tested once a week.

Mr. Stringer’s campaign said last week that he was in quarantine “out of an abundance of caution” after attending an outdoor event with Representative Adriano Espaillat on Jan. 8. Mr. Espaillat announced on Thursday that he had tested positive for the virus.

In December, Ms. Wiley said she was quarantining after she was in contact with someone who tested positive.

The candidates have for the most part moved events online, especially as coronavirus cases have risen in recent months. The test positivity rate in the city is above 8 percent.

Mr. de Blasio has been holding his news conferences online. The mayor also saw Mr. Espaillat at an event outside City Hall on Jan. 9, but decided not to quarantine; Mr. de Blasio’s spokesman, Bill Neidhardt, said there was no “prolonged close contact” between them.