MOBILE, Ala. (AP) — Alabama’s largest public school district says it will switch to virtual classes on Monday.

The Mobile County system said that so many staffers have contracted or been exposed to COVID-19 it’s difficult to keep buildings open.

The district has more than 53,000 students and 7,200 employees in the state’s southwest corner. It joins more than 30 others systems statewide that have opted for online learning since classes resume because of a surge in illness as the highly contagious omicron variant spread quickly.

More than 16,000 new cases of COVID-19 were reported this week in Alabama schools, including more than 600 in Mobile County schools.