Students clad in shorts and sunglasses spilled into George Washington University’s concrete quad this week: an annual ritual welcoming the arrival of warm weather. But beneath the sunshine loomed uncertainty.

Demetra Vernet, a biological anthropology major, said she’s anticipating a situation akin to the one unfolding at Columbia University, where officials this week canceled classes and announced plans to temporarily migrate coursework online.

“I have a one-way ticket,” Vernet, a senior, said. She plans to spend spring break in Boston but is unsure when — or if — she will return to the District.

The spread of coronavirus has unsettled campuses throughout the country. Communal gatherings are being rescheduled in an effort to prevent infections. The Ivy League canceled its men’s and women’s postseason basketball tournaments, becoming the first Division I conference to take that step.

And, on the cusp of spring break, campuses are urging students to rethink travel plans. For some, the arrival of one of the most anticipated weeks of the school year will mean saying goodbye to friends and professors. As universities make swift and consequential decisions in the name of safety, many rites of college life are under threat.

“I’d be lying if I said I think things would just resume back on course,” said Lanier Holt, an assistant professor in Ohio State University’s School of Communication. The university announced Monday it would suspend face-to-face instruction through the end of the month.

Amherst College, the University of Washington and Princeton, Stanford and New York universities have announced dramatic changes in recent days. Indiana University announced face-to-face teaching will be temporarily suspended after spring break. At Harvard University, students have been instructed to return to their homes away from campus after spring break and complete coursework remotely.

LaShyra Nolen, a first-year student and class president at Harvard Medical School, said her classes are going online as soon as Monday. Students will continue to go to clinical sites, she said, because without those hours, they can’t move to their second year.

But “this could change in the next week,” she said. “There’s this angst and nervousness I feel in the air.”

Students at GWU are in a state of limbo as they await further guidance from university leaders.

“There’s a lot of stuff up in the air,” said Jessica Baskerville, a sophomore studying journalism. “If we had to self-quarantine, would we have to go home? Could we stay on campus? Can I leave my room at all? We’re getting a lot of notifications, but it’s a lot of nothing.”

More challenges lay ahead: Seniors, on track to graduate, worry their ceremonies will be called off in the same way other large-scale events have been canceled. Students who have paid thousands of dollars in housing fees wonder what will happen if they are sent home before the semester ends.

“I’m just trying to remain calm and take things as they come,” said Kaelyn Sanders, a senior at Ohio State.

For many students, a week that typically offers a respite from stress and responsibility is now fraught with unknown risks. Memes have been spreading on social media, with students anticipating spring break spent lying on the sand or floating in pools encased in protective medical suits.

Some campus leaders have strongly advised students not to travel internationally — including, for the University of Southern California, popular destinations such as Cabo San Lucas and Cancun in Mexico – and to consider avoiding travel all together.

“If you travel internationally, be prepared for mandatory health screenings, flight cancellations, or isolation measures — including the possibility of a required 14-day self-isolation,” before returning to campus, the university warned in a message to campus.

The most challenging element is how to advise students about travel within the United States, said Sarah Van Orman, chief health officer with USC Student Health.

“It’s very complicated,” Van Orman said. There are no public health guidelines about domestic travel, with the situation changing so rapidly. USC officials sent a message to students recently advising them to look at the local situation and carefully consider any domestic travel.

Colleges are in an unusual position, said Van Orman. There’s clearly a higher risk of infections spreading in a communal living situation and in classrooms. But unlike K-12 schools that might shut down to minimize the chance of transmission of infections, “for a university, the idea of everyone leaving campus and coming back is, unfortunately, a risky situation.”

More than 60,000 students are enrolled at OSU’s main campus in Columbus, Ohio.

“These students come from every nook and cranny on the planet Earth,” Holt said. “Even if a handful of people contracted the virus, we’ve basically made a petri dish for the virus. And then we spread it when the semester ends in about six weeks, all over the world.”

Sweeping changes to campus life will hit the most vulnerable students the hardest. Those who rely on meal plans, cannot access the Internet at home or can’t afford to travel have a few days to prepare for a future that seemed far-fetched a mere month ago.

Morgan McDonald, an OSU student who relies on academic assistance, said she does not know how she will access those services from home. She has an anxiety disorder and needs extra time for quizzes and tests.

“If that can’t happen, then that causes me more anxiety,” McDonald said.

Schools are responding in a variety of ways, said Brad Farnsworth, vice president for global engagement with the American Council on Education. One way: Some residential campuses are ensuring that students who don’t feel safe traveling, particularly international students, can remain on campus with food and housing.

For now, a routine part of the academic calendar suddenly poses a multitude of challenges. Some schools have updated their advice multiple times in recent weeks.

The rapidly changing situation has sent schools scrambling.

“I thought, at some point, I’d teach a class online,” Holt said. “I just didn’t think it would be next week.”

Karen Weintraub in Boston contributed to this report.