Last week, Amy Morrison was planning for the possibility that coronavirus might affect her campus — a prospect facing college presidents throughout the nation.

On Saturday, she abruptly learned her school was right in the thick of it: Lake Washington Institute of Technology students and faculty had visited a nursing home near Seattle. Cases of covid-19, the disease caused by the coronavirus, had just been confirmed there.

By Sunday, Morrison had announced the 6,000-student campus would close. On Monday and Tuesday, workers cleaned and disinfected the school, and the more than 20 students and faculty who had possibly been exposed were advised to remain in isolation for two weeks.

The campus briefly reopened Wednesday — before closing again that night. A faculty member had tested positive for covid-19, Morrison announced, and the campus would close through the weekend.

In New York, Yeshiva University’s president announced Wednesday that a student had tested positive for covid-19 and classes would be canceled at their Washington Heights and Midtown Campuses until after March 10.

On Thursday, Everett Community College, near Seattle, closed and its president announced a student had tested positive for covid-19.

Colleges and universities first confronted coronavirus as a problem overseas: They have shut down study-abroad programs, closed campuses in China and worried about the effects on international students and overseas research. But as the number of confirmed infections in the United States surged past 100 this week, with 11 deaths as of Wednesday night, many schools are ramping up planning on their campuses, bracing for the possibility of a more profound and direct hit.

College leaders are crafting and revising contingency plans with an eye toward the effect the outbreak could have on students and employees, on research and on major events such as the National Collegiate Athletic Association basketball tournament this month. There is talk of canceling meetings, restricting travel and what to do if cases surface on campus.

College health officials began intense work on preparations last month “like we were shot out of a cannon,” said Jean E. Chin, who leads an American College Health Association task force on coronavirus.

On Wednesday, the group released guidelines for schools, warning the virus was a risk for colleges because of travel by people from schools and because of the potential for rapid transmission on campus. The group advised student health centers to quickly prepare for potentially infectious patients.

Because colleges are such complex organizations, with varied missions and constituencies, the planning is particularly complicated, several experts said.

Some spring and summer programs are being canceled, said Preeti N. Malani, the chief health officer at the University of Michigan and a doctor specializing in infectious diseases.

Officials are wondering whether they may need additional housing over the summer for students unable to return home, and the medical center is bracing. “We’re trying our best to be prepared for large numbers of patients,” she said. “We hope that doesn’t happen, but we need to be ready.”

For residential campuses, there are the challenges inherent in communal living. “We all know how college students are,” Chin said. “They share stuff. They share secretions. They share drinks. They share phones. They share stuff.”

Many campuses are wondering how they would implement a directive to quarantine people, said André Le Duc, chief resilience officer and associate vice president for safety and risk services at the University of Oregon. Le Duc, a leader of a network of hundreds of college officials sharing questions, ideas and resources about emergency planning online, said officials are weighing how they would handle a disruption to classes if that was necessary.

At the University of Oregon, more than 100 people are working on outbreak contingency planning, he said, including some focusing on travel advisories, housing, athletics and academic continuity.

More than 23,000 people have signed an online petition calling on the University of Washington to close its Seattle campus to prevent people from spreading the virus in the school’s dorms, classrooms and dining halls. The university has had no confirmed infections, but deaths related to the coronavirus in the region sparked fears among students and others that infections might already be spreading there.

The campus never really closes, said Victor Balta, a spokesman for the public university, which includes a hospital and houses several thousand students. Public health officials have not advised the school to shut down or cancel large events.

But for days, university leaders have been planning possible responses to the outbreak, including suspending classes and quarantining students, and trying to answer the many questions people have. Spring break is approaching, and officials are asking people to be mindful of health advisories and aware some countries have abruptly imposed travel restrictions.

The University of Washington already has some emergency relocation housing for students who might need to be in isolation because of an illness, said Denzil J. Suite, vice president for student life, and they could take on 50 “or maybe 100 in a pinch,” he said, and deliver food if quarantines became necessary.

University of Washington faculty members have experience shifting to online instruction — such as when a major snowstorm last year abruptly halted classes — and school officials are working to scale that up and test technology for the potential of heightened demand.

At the Lake Washington Institute of Technology, as staff work to disinfect the campus and school leaders work to determine who may have been exposed to the virus, Morrison told the campus in a message Wednesday that “this continues to be a very fast-moving situation.”

She has advice for other college leaders: Keep an updated list of students and faculty who work in medical settings, and know how to reach them. Keep the communications staff close, because crucial information might have to be shared quickly. If the coronavirus has not surfaced in their community, she said, contact the public health department, hospitals and government officials — to be ready, just in case it does.