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 say most of the cases are linked to the University of Illinois campus.
Director of the McKinley Health Center Dr. Robert Palinkas says mumps outbreaks happen periodically on campus, but he says the current outbreak is the largest in more than a decade.
Palinkas says the university is working to isolate students who have mumps.