Public health officials are investigating an unusually large outbreak of shigellosis, a bacterial gastrointestinal illness that has sickened 25 people in Onondaga County.

The county Health Department announced there have been 15 laboratory confirmed cases and another 10 probable cases of shigellosis. More than half the cases involve children. Two of the people infected have been hospitalized and some others have been treated in emergency rooms and urgent care centers, said Dr. Cynthia Morrow, Onondaga County’s health commissioner.