Bluewater Health has imposed visitor restrictions on its Mental Health Inpatient Unit.
Officials say infection control procedures have been implemented in response to fewer than five patients developing gastrointestinal symptoms.
The unit currently has 26 patients and will be restricted to two designated visitors per patient to prevent further transmission. The visitors will have to wear gowns, masks with eye protection and gloves, and will be prohibited from visiting patients in other areas of the hospital for the duration of the outbreak.
The restrictions will continue to be in place until all patients are symptom free for 72 hours.
Lambton Public Health has been notified.
The hospital says members of the public should continue to come to Bluewater Health for scheduled tests and procedures.