Hundreds of colleges have reversed or altered their reopening plans in the past several weeks after taking stock of COVID-19 testing availability, student and faculty safety concerns, state regulations and the worsening public health crisis.

Through May, June and July, many colleges announced in-person reopening plans that included social distancing protocols, mask-wearing requirements, low-density living arrangements and regular testing for students and employees.

As many reopening plans were finalized, the coronavirus pandemic surged across the United States. Northeastern states home to the first viral hotspots — including New Jersey and New York — have largely quelled their worst outbreaks, but case counts have spiked in the southern and southwestern states over the past month. Case counts are swelling in California and reaching new peaks in Colorado, Louisiana, Washington and Wisconsin. As of Tuesday, the United States had more total cases than any other country in the world and the largest share of cases as a proportion of the country’s population.

Many colleges planning to bring students back to campus for the fall semester have reversed course entirely and opted for online-only instruction. Smith College president Kathleen McCartney announced last week that the college would not bring students back to campus this fall, citing “new scientific evidence, as well as recent and troubling trends nationally and in Massachusetts.” Days later, Mount Holyoke College in Massachusetts announced that it would not re-open for in-person instruction this fall.

Berklee College of Music in Boston said July 22 that it would conduct a virtual fall semester. This was in part due to travel restrictions and the difficulty in getting international students back on campus, said Betsy Newman, Berklee’s senior vice president for student enrollment and engagement.

Goucher College outside of Baltimore and Salem College in North Carolina have also scrapped in-person instruction plans.

Some colleges have only delayed their in-person start dates. The University of Maryland announced Monday that it would delay all in-person undergraduate instruction for two weeks until Sept. 14, citing the high COVID-19 positivity rate in its home county, Prince George’s County. Brown University announced Tuesday that it would bring a significant number of students back to campus in October at the earliest, delaying previous plans. Brown is still determining when and how many students will be able to return, if any. The decision is notable after Brown’s president wrote an opinion piece in The New York Times in April arguing for campuses to reopen for several reasons, including that low-income students face barriers to learning remotely, that the economy depends on it and that colleges need the revenue.

Previously, the University of Maryland and Brown University were planning to reopen in-person at the beginning of the fall semester.

Chapman University in southern California announced recently that it would begin the fall semester with online instruction. The university had been waiting on further guidance from California governor Gavin Newsom and made the decision to go online as the public health situation in the state worsened.

Chapman’s decision, though crucial for students’ and employees’ safety, will contribute to the university’s growing deficit.

“These are very expensive propositions for universities,” said Daniele Struppa, president of Chapman. “Between lost revenue and additional expenditures, we are looking at a deficit of $100 to $110 million. So that’s a significant amount of money.”

Winthrop University learned that containing the spread of COVID-19 on campus would be difficult, and its leaders opted to delay in-person instruction until Sept. 7 out of an abundance of caution. Two students tested positive for COVID-19 over the summer.

“We learned that even with small numbers of students, community spread is going to happen when the numbers across our state were steadily increasing. Two students did test positive and were treated,” Judy Longshaw, a spokesperson for the university, wrote in in an email. “One of the important takeaways for us was that sending students home if possible for quarantine and/or isolation is our preference. Sick students need care, and we are not staffed to provide the level of care some students who come down with the virus may need.”

Miami University in Ohio, Illinois State University and the University of California-Merced have also delayed in-person start dates, among many others.

The August changes will affect many students who were planning to return to campuses this fall. For some, it brought feelings of déjà vu.

Benjy Renton, an East Asian studies student and rising senior at Middlebury College, was in China in January when the COVID-19 outbreak worsened in the country.

“I saw things go wrong the first time, and I had to see it go wrong the second time,” he said.

Renton has been tracking colleges’ plan reversals and alterations since the University of Southern California announced in early July that a majority of undergraduate instruction would be held online. The university has since delayed students’ return to campus and said that all instruction will be held online for at least part of the fall term.

The bulk of reopening change announcements were made in late July and early August, according to Renton’s data. Last week, more than 40 colleges released changes to their reopening plans. Half of the colleges Renton has documented cite the ongoing public health crisis as a leading reason for the changes. Student health and safety, testing availability and COVID-19 transmission on campus were also cited in some cases.

Renton has focused on tracking two trends: when colleges announce changes and where colleges are announcing changes.

Peer institutions in similar geographic areas tend to follow each other’s lead, he said. For example, in Washington, D.C., George Washington University announced July 27 that it would reverse its plans and conduct all instruction online in the fall. Georgetown University followed suit two days later, and American University announced the same on July 30.

Location has also played a role. New Jersey for example has strict requirements about what conditions need to be met before colleges can reopen. The College of New Jersey, Princeton University, Saint Peter’s University and Rowan University are conducting all or nearly all classes online.

If colleges do bring students back, Renton is not optimistic about how long they will be able to stay open in-person this fall. He compares residential campuses to aircraft carriers, cruise ships and nursing homes — situations where people live in close proximity.

“All the ones that we’ve seen just don’t go well. Theoretically, all the science is telling us no,” Renton said.

As of Tuesday, Middlebury College is planning to bring students back in the fall. Renton intends to return to campus.

“I’m going back for now,” he said. “From data that we got last night, most students intend to return to campus. I think we’ll hopefully just hope for the best, and hope that we’re able to stay as long as we can.”