Lambton Public Health declared a COVID-19 outbreak at Marshall Gowland Manor on Friday after a staff member tested positive for the virus.
The health unit said residents of the Sarnia long-term care home, and their families, have been notified.
The employee last worked at the home on Thursday, January 14, and is not symptomatic. The positive case was detected though routine staff testing.
Residents were being tested for the virus Friday, and none of them currently have to be isolated.
Lambton County General Manager of Long-Term Care Jane Joris said the health and safety of long-term care residents and staff is a top priority.
"We are working closely with Lambton Public Health and following the guidance that is provided to us," said Joris. "We are diligently following all of the policies and protocols put in place by the Ministry of Health and the Ministry of Long-Term Care to prevent the spread of COVID-19 in our Homes."
Lambton Public Health said it's working on contact tracing, and said it will contact those impacted to provide guidance.
A long-term care or other communal living setting outbreak is declared facility-wide when one or more lab-confirmed COVID-19 case(s) in a staff member or resident and possible exposure to others in the setting has occurred.
There are 127 residents at Marshall Gowland Manor, and nearly 200 staff members.