The hospital — along with the Simcoe Muskoka District Health Unit — declared the outbreak Tuesday afternoon because of an increase in the number of hospital-acquired cases in the last 30 days.
There have been five confirmed cases reported in different areas of the hospital.
Officials say the hospital is taking measures, including stepped up cleaning in affected areas, minimizing patient transfers to multiple rooms, and an enhanced focus on hand hygiene.
There are no visiting restrictions being implemented but visitors are being asked to wash their hands thoroughly when entering and leaving patient care areas.
The outbreak will remain in place until it there have been eight consecutive weeks at or below a baseline of one case per month.