With no systematic effort to trace or advise the hundreds of guests at the Rose Garden ceremony and other events in the surrounding days, many made their way home and resumed their busy schedules, according to interviews with more than 40 people who attended events with the president between Sept. 25 and Oct. 1, when Trump announced he had tested positive.

Experts said the fallout, driven largely by individuals forced to make their own choices without clear instructions from a central authority, is emblematic of the nation’s response to the pandemic and helps explain why the virus remains uncontained nearly 10 months after it first arrived in the United States. The infection of Trump and those around him was, even more starkly, a window into an attitude of invulnerability and indifference that surrounds the president.

One of the people ensnared in the outbreak was Ronna McDaniel, the chairwoman of the Republican National Committee, who mingled with donors at a Sept. 25 event headlined by Trump at his hotel in Washington. She tested positive for the virus five days later but only made her diagnosis public on Oct. 2 after informing the president that morning. A person close to her said she attempted to reach the president sooner but was unable to talk to him.

For 36 hours after her diagnosis, the RNC made no attempt to inform donors who had attended the extended, indoor fundraiser with McDaniel. Only on Oct. 2, after the president had also tested positive, were attendees told they might have been exposed.