The presidents of Brigham Young University and Utah Valley University threatened Tuesday to close their campuses for the rest of the semester if students keep refusing to follow health guidelines — especially as cases of the coronavirus keep climbing at both schools.

In a joint letter Tuesday to all students, the leaders say that they’ll be watching both behavior and the daily virus numbers over the next two weeks as the cities of Provo and Orem transition backward to an “orange” or moderate risk level. And, “if circumstances do not improve,” they will take action.

“This may include a two-week quarantine, closing campuses to the public or a complete retreat to all-remote instruction for the rest of the semester,” said BYU President Kevin Worthen and UVU President Astrid Tuminez in the message. “Please be wise. Your individual choices will make all the difference.”

The two schools have become part of the epicenter of the outbreak in Utah County, where residents make up about 20% of the state’s population but have lately been accounting for 40% of the COVID-19 cases. Most of those are falling in the younger age group of 15- to 24-year-olds. And some have been pointing to school reopening for driving the spread.

At BYU in Provo, which is owned by The Church of Jesus Christ of Latter-day Saints, school officials had reported 1,014 cases as of Tuesday on the campus of 33,000 students. That’s the highest of any college in the state.

At nearby UVU in Orem, there have been 198 cases. But the school hasn’t updated its numbers since Sept. 14. The campus there, though, is the largest in the state, with nearly 42,000 students.

“This is both alarming and unacceptable,” the two university presidents said.

Based on an order from the governor Tuesday, Provo and Orem will fall in the “orange” category for risk beginning Wednesday at 11:59 p.m., backpedaling from the lower “yellow” level. The transition doesn’t change anything for classes, specifically. And, for now, all sports will continue — but without spectators.

The leaders write in their letter that they want students to continue to be able to take classes in person. In order to do so, they say: “Behavior must change.”

Some have blamed the spread on large dance parties in both communities that are advertised to college-age students and organized by the company Young/Dumb. Social media pictures from those events show what appears to be hundreds of kids crammed together.

Additionally, there has been general pushback against following the health and safety policies at both institutions — and in the county, as a whole — particularly around wearing masks. BYU said last week that it disciplined 15 students who “refused to follow these requirements.” Two later withdrew from the university in protest.

Worthen and Tuminez said that ignoring the guidelines is not an option if the schools are to remain open.

“We’re concerned not only for your well-being, but also for those in the local community who are affected by the trends we’ve seen in the last week,” they say.

They then instruct students to stay home except when going to class, work, church or other essential places. They encourage everyone to limit social interactions. If a student is feeling sick, the presidents said, they should stay inside. If they’ve been exposed to the virus or tested positive, they need to quarantine.

Worthen and Tuminez add: “We expect you to follow all safety requirements on campus and all state and local mandates off campus.”

Gov. Gary Herbert applauded the joint letter during a Tuesday news conference, saying that he hopes it “can modify their behavior in a good way.”

But House Speaker Brad Wilson criticized students in a separate statement, saying they are to blame for the change back to “orange” and the impact that will have on businesses.

“The citizens of our state invest heavily in our universities, which serve as the training grounds for those who will lead our state in the years and decades to come," Wilson said, "and we rightfully call upon our college students to rise to the occasion to protect themselves, vulnerable members of our community, and our economy.”