Many U.S. colleges and universities are preparing to reopen for the fall semester, with in-person classes scheduled widely. It is understandable that many students, parents and college officials are on edge.

Science is on their side, in a way. COVID-19 seems to be most dangerous for older people with pre-existing medical conditions. Younger people can contract the virus, but many demonstrate few, if any, symptoms.

A wakeup call may be necessary for many younger people, however. They are not safe. Well over 10% of the more than 146,000 Americans killed by COVID-19 were in the 15-24 age group, the Centers for Disease Control and Prevention reports. Being less susceptible to the disease does not mean being safe from it.

Higher education officials also are aware of the danger of hundreds of thousands of students leaving home to return to campus — then going home, possibly carrying the virus with them to infect mom, dad, grandma and grandpa.

So restrictions on attendance, some quite stringent, are being implemented at most campuses.

Whatever the restrictions on students, they simply must be enforced strictly. Reopening colleges and universities cannot be permitted to become a lesson in how to make an already severe epidemic explode.