Not since the attacks of Sept. 11, 2001, has a crisis enveloped so much of the economy so quickly. Broadway is dark. The college basketball tournaments are canceled and professional sports are on indefinite hold. Conferences, concerts and St. Patrick’s Day parades have been called off or postponed. Even Disneyland — which stayed open through a recession a decade ago that wiped out millions of American jobs and trillions of dollars in wealth — is shuttered.

“This hits the heart of the economy, and it hits the economy on all sides,” said Diane Swonk, chief economist at Grant Thornton. “It’s not just that we’re slowing down things. We’re actually hitting the pause button, and there is no precedent, there is no mold for that.”

The effects are being felt even in places that the outbreak itself has not yet reached. Maine had not had a single diagnosed case of the virus when Ms. Hornor learned Wednesday that Bowdoin College, which accounts for 80 percent of her business, was calling off in-person classes and sending students home. Yet by midday the next day, she had lost 84 bookings, with more cancellations all but certain. At a somber staff meeting on Thursday, she told her 10 employees that she would try to avoid layoffs but that cuts in hours were inevitable.

“I have people who rely on me to be able to pay their rent,” she said. “Not only do I have no money coming in, I’m kind of hemorrhaging cash in terms of refunds for everyone.”