The Illinois Department of Public Health says the state has 73 known mumps cases right now and more than two-thirds are in Champaign County.
State and local health officials say the number of cases in the Champaign area is at 50 and could climb.
Health officials tell the News-Gazette that most of the cases are linked to the University of Illinois campus. And thousands of students who are away are expected to be back on campus in the next few weeks for fall classes.
Dr. Robert Palinkas is director of the McKinley Health Center. He said mumps outbreaks happen periodically on campus. But he said the current outbreak is the largest in more than a decade.
Palinkas said the university is working to isolate students who have mumps.