University of Virginia officials said Thursday that widespread noncompliance with campus health guidelines is driving an explosion of coronavirus cases at the school.

There are 779 active cases — including 18 among employees — on and around the Charlottesville campus, more than half of which were reported this week, according to university data.

On Tuesday, 229 new cases were reported, the highest single-day count for the school. That number fell slightly Wednesday, to 174 cases.

The campus is also dealing with a variant of the virus first identified in Britain, but officials have not yet said how many cases are tied to the new strain.

The increase in cases comes as coronavirus cases have been falling across the greater Washington region in recent weeks. In Virginia, the ­seven-day average number of new infections statewide stood Thursday at 2,411 — less than half the highs that were recorded in January.

The recent surge at U-Va. triggered new safety restrictions this week — including a ban on in-person­ gatherings and the closure of several campus buildings — that university officials said could last until Feb. 26. Leaders will consider suspending the new restrictions if conditions improve.

In-person classes are set to continue. They were not held Thursday because of the weather.

The sharp increase in cases come after a weekend of fraternity and sorority rush events, but university officials said the Greek organizations are not solely to blame.

“Like all other students and organizations, those organizations were permitted to gather in groups of six or fewer as long as everyone was wearing masks and spaced at least 6 feet apart,” officials said in an email that was sent to students. “Transmission and noncompliance are widespread across our community.”

The university’s Inter-Fraternity Council, a student-run organization that oversees 32 fraternities on campus, encouraged chapters to host virtual events, but in-person activities still occurred, student leaders said in a statement. The group of fraternity leaders said members met nightly during the recruitment process to address reports of coronavirus policy violations, some of which allowed the group to cancel events that would have breached safety protocols.

But some students think in-person recruitment events should not have been permitted at all, given the risk that comes with gatherings of any size, said Ellen Yates, president of the university’s student council.

“Activities like that, where you have a lot of people in small spaces, in quick succession, are inevitably going to breed illnesses during a regular year,” Yates said. “There is a degree of entitlement in thinking that could work.”

The gatherings have not been limited to Greek organizations, U-Va. officials said. And as the virus continues to spread, the campus is urging students to report their peers who gather in large groups or shirk other safety guidance.

“We are a community — and bringing our case numbers down will require all of us to sacrifice over the next eight days and keep our focus for the rest of the year,” officials wrote to students.

The 10-day restrictions announced Tuesday, designed to limit students’ movement around campus, are taking a toll on students already stretched thin by the pandemic.

“I know a lot of students who are very worried and are reducing their activities outside accordingly,” Yates said. “I know some students who are just incredibly frustrated, who feel the restrictions are deeply unfair.”

University President Jim Ryan, along with other U-Va. officials and medical experts, will host a virtual town hall about the situation Friday afternoon. Students, employees, parents and community members are invited to attend.