CHICAGO (CBS)—There have now been two confirmed cases of mumps at Lewis University, and other Chicago-area colleges are reporting cases. 

That’s in addition to 13 probable cases at the school’s Romeoville campus.

Students at Lewis University recently started hearing about mumps cases, but the word ‘outbreak’ started being used a few days ago after several possible cases came up.

University officials have since started requiring students to show proof of vaccinations.

A Lewis University spokesperson said 300 booster shots were given to students and staff on campus to help keep the virus from spreading.

Cases have also been reported at Columbia College and Loyola University.