Four recent cases of E. coli may be connected, according to a report from The Associated Press.
The DuPage County Health Department is currently investigating whether everyone with the infection ate at the same restaurant, the report said.
All E. coli patients were treated this week at Advocate Good Samaritan Hospital in Downers Grove, according to AP.
Symptoms of the disease, which is potentially deadly, include stomach cramps and diarrhea. It is caused by contact with contaminated water, food, animals or people, the report said.