E. coli at a Lemont, IL day care is responsible for making 21 children and one adult ill in an outbreak that began in early February.
The Cook County Health Department has ordered tests for all children and adults at the KinderCare Learning Center, 12404 Archer Ave.
Officials allowed the day care center to remain open so the children have a place to go and not possibly carry the bacteria to other centers.
Three children associated with the outbreak – linked to a lack of handwashing – were hospitalized but have since been treated and released.
The remaining children carrying the bacteria are all under the age of 5. They, along with the adult, have been sent home along with anyone experiencing diarrhea until tests for the bacteria turn up negative twice within 24 hours.
A person who has no symptoms could still test positive for the bacteria, the department warned.
KinderCare has stepped up its efforts to sanitize the center, including adding enhanced cleaning, additional staff to monitor handwashing, and hiring a certified nurse.