WILMINGTON, Del. (AP) — At least three people connected to Joe Biden's presidential campaign have tested positive for the coronavirus, leading the campaign to suspend in-person events for vice presidential nominee Kamala Harris through Monday.

Biden is not altering his public schedule, his campaign said Thursday, because he had no direct exposure to the individuals who tested positive, as defined by the Centers for Disease Control and Prevention.

It’s the Biden campaign’s first major coronavirus scare, after months of safety precautions that drew mockery from President Donald Trump, even after he, first lady Melania Trump and others contracted the virus themselves. The Democratic campaign’s cautious reaction underscores the differences in how the rival camps have approached the pandemic, both in terms of preferred government response and in the candidates’ personal protocols.

Biden's campaign announced two positive cases Thursday morning, identifying Harris' communications director Liz Allen and an unnamed member of the flight crew for one of Harris' recent campaign trips. The campaign announced a third case Thursday afternoon as part of its contact tracing efforts from the first two cases.

The third individual is an aviation company employee who was on Biden's plane for trips to Ohio and Florida earlier this week but who entered the back of the plane and sat far away from Biden, according to the campaign.

Harris and Biden, meanwhile, spent several hours campaigning together in Arizona on Oct. 8, when the first two people who tested positive were on a flight with Harris. Both candidates have tested negative for the coronavirus multiple times since then, including on Thursday. Everyone on the Biden campaign plane is required to wear a mask.

Trump, speaking without a mask at a crowded outdoor rally in North Carolina on Thursday afternoon, offered his best wishes to Harris and reiterated his skepticism of wearing masks.

“We worry about her. I'm very concerned about her,” he said, later adding: “Masks, no masks, everything, you can do all you want, but you know, you still need help."

The travel suspension interrupts the Biden campaign’s aggressive push across a wide battleground map, including North Carolina and Ohio, with less than three weeks to go until Election Day.

Harris was set to encourage early voting Thursday in North Carolina. Her Friday trip to Cleveland would have been her first to Ohio as the vice presidential nominee and would have taken her into the metropolitan area with the state’s largest concentration of Black voters.

Harris will continue virtual campaigning, including fundraisers previously scheduled for Thursday, Friday and Saturday.

The senator's brief hiatus from the trail comes as Trump ramps up his own travel after he, the first lady, his campaign manager and several White House staffers contracted the virus.

Biden campaign manager Jen O'Malley Dillon told reporters Thursday morning that under CDC guidelines, there was no need for the candidates to quarantine, although she said Harris and her husband, Doug Emhoff, would suspend travel for several days “out of an abundance of caution.”

“Neither of these individuals had any contact with Vice President Biden, with Sen. Harris or any other staff member since testing positive or in the 48-hour period prior to their positive test results,” O'Malley Dillon said.

Harris followed up in a statement saying she'd be “transparent with you about any test results that I do receive. In the meantime, remember: wear a mask, practice social distancing, and wash your hands regularly. It is possible to stop the spread.”

O'Malley Dillon announced the third case late Thursday afternoon. She said Biden's medical advisers recommended against a quarantine because of the distance between Biden and the third individual who tested positive.

Harris and Biden spent several hours together on Oct. 8 through multiple campaign stops, private meetings and a joint appearance in front of reporters at an airport. They were masked at all times in public, and aides said they were masked in private, as well, including on all flights.

Biden will attend an ABC News town hall on Thursday airing live at 8 p.m. EDT, and he will proceed with his planned travel Friday and through the weekend.

O'Malley Dillon said all campaign staff members on the Oct. 8 flight have been tested at least twice since then. All tests have been negative, she said.

The campaign became aware of the first two positive tests Wednesday night, O'Malley Dillon said. Harris had opted earlier this week to attend virtually — rather than in person — the Senate Judiciary Supreme Court confirmation hearings for Amy Coney Barrett, after some of her GOP Senate colleagues tested positive for the coronavirus or disclosed their exposure to others who had tested positive.

Biden's campaign has taken the coronavirus seriously, drawing mockery from Trump and Republicans, even as the White House deals with the fallout of its virus outbreak.

The Democratic ticket's campaign events are socially distanced and require participants to wear masks. Staff often set chairs inside white plastic circles to denote 6 feet (1.8 meters) of distance. During a recent indoor speech at a North Carolina event for Harris, reporters were given and asked to wear KN95 masks.

Biden and Harris typically keep their masks on when speaking indoors. Both travel on planes with a small number of staff and Secret Service. For Harris' travel, a second plane carries the rest of the staff. For Biden, a second plane carries the traveling press corps.

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Associated Press reporters Kathleen Ronayne in Sacramento, Calif., Alexandra Jaffe in Washington and Thomas Beaumont in Des Moines, Iowa, contributed to this report.