Two staff members and two residents at the Southampton Care Centre have tested positive for group A Strepococcus.
They were tested after an elderly resident died earlier this month at the Seniors facility.
The Grey Bruce Health Unit swabbed all 88 residents and 92 staff members.
Manager of the Infectious Diseases Program Karen Sweiger says all four are being treated with antibiotics even if they are not showing signs of illness.
The Southampton Care Centre has not been closed to visitors and there was no outbreak according to Sweiger.
She says there is no risk to the general public.
Sweiger says Group A strep is found in the nose and throat of anywhere from five to 30 per cent of healthy children and one per cent of adults — who may not even show symptoms of illness.
