NEW YORK (NYTIMES) - It was a tough fall semester for many US colleges and universities, with declining enrollment, cancelled classes and sporting events, widespread Zoom fatigue and enough coronavirus-infected students nationwide to fill 3 1/2 Rose Bowls.

But many university officials say that lessons from the fall will allow them to do something many experts considered unthinkable a few months ago: bring even more students back onto campus in January and February, when classes resume for the spring.

The University of California, San Diego, for instance, is making room for more than 11,000 students in campus housing - about 1,000 more than it housed in the fall. The University of Florida is planning to offer more face-to-face classes than it did before the pandemic. And Princeton University, which let only a few hundred students live on campus last semester, has offered space to thousands of undergraduates.

The determination to bring back more students, even as the pandemic is surging in many states, partly reflects the financial imperative to have more students paying room and board, as well as the desire to provide something resembling a college experience.

But there is also an emerging confidence among at least some college administrators that they have learned much about managing the pandemic on their campuses. Test aggressively. Contact-trace assiduously. Maintain mask rules and social distancing. And don't underestimate students' willingness to obey restrictions.

"What makes me optimistic is, we had the virus in our community, and each time we did, we were able to stop transmissions dead," said Mr David Greene, president of Colby College in Maine, which brought its whole student body back in the fall using aggressive health measures and plans to do the same again next semester.

Experts said a major test of whether colleges learned the right lessons would come in January and February, when students travel back to school from home.

"The disease is a lot more widespread now than it was" in the fall, said Dr Tom Frieden, who ran the Centres for Disease Control and Prevention (CDC) during the Obama administration and is now president of a global health initiative to prevent heart disease and epidemics. "When people travel, the virus travels."

Since the start of the pandemic, campuses have weighed the financial and social benefits of business as usual against the terrifying risk of Covid-19. Young people are statistically less likely than older adults to become severely ill or die from the infection, but they have turned college towns into Covid-19 hotspots. Schools and the communities around them have also enforced public health rules inconsistently.

Many institutions are choosing not to bring back more students, planning instead to hunker down over the winter as infections mount and the nation awaits a vaccine. The University of Michigan, which spent a rocky fall trying to keep thousands of students on campus, has told most of its students to stay home and study remotely next semester. The California State University's 23 campuses have concluded that sticking with remote classes is the safest approach for the spring.

But other schools, and some experts, are asking: Safe compared to what?

"Having students return to campus to live under the imperfect supervision of college administrators is risky," said Professor A. David Paltiel, a health policy and management expert at the Yale School of Public Health. "But having students stay home to live under the imperfect supervision of their parents and families is also risky."

That argument has been particularly compelling for schools that managed the fall with relatively minimal infections - and the schools that watched and learned from them. Cornell University expects about 19,500 students will be living on or around its Ithaca, New York, campus next semester, more than 80 per cent of enrollment and about 1,500 more students than were there during the fall.

Brown will roughly triple and Harvard will about double the number of students in campus housing in the new year. Wheaton College in Norton, Massachusetts, will add about 100 students to the approximately 1,200 who were living on campus in the fall. It also plans to reestablish its study abroad programmes, according to a school spokesperson.

Students have also proved more conscientious than the public may think, administrators said. The culture of fraternities, big sports and big parties remains a challenge, but at many schools, students themselves reported the majority of health violations.

"When this started, the premise was that students would not and could not behave responsibly," said Mr Michael Kotlikoff, Cornell University's provost. "I think we've proven that this is not so."

Many university officials say they are also increasingly confident that the virus is not being transmitted in classrooms, where professors are enforcing mask-wearing and social distancing rules.

"We have not had a single case that we can trace to a classroom," said Mr Mike Haynie, vice-chancellor for strategic initiatives and innovation at Syracuse University. "It happened in communal living situations and in gatherings that took place off campus."

Mr Haynie cited a study of 70,000 undergraduates at Indiana University, which found that the more classes a student took in person, the lower the likelihood that student would become infected with the coronavirus.

"The spread is in teacher break rooms, in fraternities and sororities," Dr Frieden said. "It's not even in organised sports, but in locker rooms before and pizza parties after."

Instructors at other schools have been a harder sell. At the University of Florida, faculty have filed grievances over the school's decision to offer 5,394 sections of face-to-face classes, 72 more than were offered last January, before the pandemic hit the United States.

Concerns have persisted even though the school, which offered only optional testing this fall when it invited its 50,000 students back to campus, will expand its testing regimen, requiring that all students living on campus or taking classes in person be tested every two weeks in the spring.

Some faculty are also revolting at the University of North Carolina at Chapel Hill. The university sent most students home a week after classes began in August because of an outbreak but is now proposing to bring 2,000 students back to campus residence halls on top of 1,500 who were allowed to stay during the fall for hardship reasons. It will also offer about 1 out of 5 classes in person in the spring semester.

This month, about 70 faculty members signed an open letter, published in the student newspaper, that predicted a repeat of the fall debacle. "We have every reason to expect that the university will - once again - be overwhelmed by infections when classes resume," the letter said.

But the university's president, Mr Kevin Guskiewicz, said he was confident the university could pull it off. "We're working from a different starting place than we were in the fall," he said.

The value of aggressive coronavirus testing has been one of the major lessons of the fall. "We changed our testing protocols substantially over the semester," said Mr Michael Fitts, Tulane's president. "At one point, we moved it up to three times a week, and we found that was very effective, and we will continue that in the spring."

Tulane has access to two testing machines through its medical school, which can conduct 3,000 tests a day and have results back in 12 hours. "I will say our positivity rate was much lower than New Orleans," Mr Fitts said of the university, which calls the city home.

Most college officials do not expect a vaccine to be available for students in the spring term. But many universities, like the University of Kentucky, are planning to be integrally involved in the distribution of vaccines through their health systems, which will position them for providing it on campus when the time comes.

Although a vaccine might seem like the light at the end of the Covid tunnel, it will also pose a new challenge for university administrators, said Ms Crystal Watson, senior scholar at Johns Hopkins Center for Health Security.

"Will they make it mandatory for students, staff and faculty?" she asked. "If not, will vaccination be required for some type of the population but not others? That's a big open question."

Ms Watson said that however far colleges have come, there is still a large gap between the wish for normalcy and the reality. "Right now it looks so different from what a traditional campus would look like," she said. "The students are getting such a bad deal this year. It really stinks."