Public health officials are investigating a sharp increase in the number of mumps cases recorded in central Illinois.
There have been 52 cases of the viral infection reported in Morgan and Sangamon counties in the last month, the State Journal-Register in Springfield reported.
There were just 26 cases reported in all of Illinois in 2013.
"This spike is unusual for us. It’s definitely more than what we would see in the course of a regular year," Jim Stone, the director of the Sangamon County Department of Public Health, was quoted as saying.
So far this year, there've been 65 cases reported across the state, including the cases from Morgan and Sangamon counties. Mumps has also been reported in Fulton, Greene, Champaign, Cook and Will counties. The cases are mostly in adults.
Mumps can cause swelling of the salivary glands, along with fever, headaches, muscle aches, tiredness and loss of appetite.