Coronavirus cases are rising at colleges around the nation with the fall semester just getting underway, alarming school officials and prompting them to reevaluate COVID-19 guidelines for students.

Of the 25 hottest outbreaks of COVID-19 in the U.S., communities packed with college students account for 19, an analysis by USA Today released on Friday indicated. Colleges across the country topped the list, from James Madison University in Harrisonburg, Virginia, to Washington State University in Pullman, and from Central Texas College in Killeen to Georgia Southern University in Statesboro.

The analysis comes as the U.S. has recorded more than 6.4 million coronavirus cases and 192,000 COVID-19 deaths. Among top college towns on the list like Harrisonburg and Pullman, confirmed cases increased last week 25% and 34%, respectively.

In Oxford, Mississippi, the state’s flagship university appeared to be doing well in mitigating coronavirus on paper, recording 430 confirmed cases since the first day of classes Aug. 24. However, data from Lafayette County show it had one of the highest per-capita rates of infection in the nation, with 1,053 cases per 100,000 people in the last two weeks, the analysis noted.

“Most students are trying to do the right thing,” Oxford Mayor Robyn Tannehill said. “Maybe they’re just very much underestimating the danger in large social gatherings.”

Other universities and city officials don’t appear to have as much faith in students, citing partying and Greek life as superspreaders of the virus.

“We are having a significant issue with a small number of students, and we have disturbing information stemming, frankly, from the fraternities in particular,” University of Tennessee Chancellor Donde Plowman said in an online address to students and staff.

Similar problems fueling the spread of COVID-19 are unfolding at schools like Indiana University, the University of Wisconsin at Madison and the University of New Hampshire.

“Let me be clear: This is reckless behavior and the kind of behavior that undermines our planning and will lead to us switching to a fully remote mode,” University of New Hampshire President James Dean Jr. said in a statement following a campus fraternity party that hosted around 100 people without masks.

Many schools have ordered exposed students to quarantine for two weeks to stop the spread while others have imposed much stricter measures. Northeastern University in Boston dismissed 11 first-year students for violating social distancing rules.

In response to coronavirus outbreaks on campus, Dr. Deborah Birx, who heads the White House Coronavirus Task Force, urged colleges to secure students who test positive for coronavirus on campus, rather than sending them home and to spread the virus further.