Middlesex London Health Unit reports show that a person tested positive Thursday at Chelsey Park in London.
Two cases are being dealt with at the Grand Wood retirement residence, where the administration of the establishment claims that the people are isolated.
On Wednesday, the Strathroy Seasons Retirement Community had someone tested for the virus.
At Henley Place, a resident was sent to hospital with a confirmed case, while a second person was diagnosed earlier in the week.
Across the province, the situation in nursing and retirement homes is dire. At least 40 people have died from complications from COVID-19.
Earlier in the week, public health units told Radio-Canada that at least 41 facilities in Ontario were experiencing an outbreak.
An outbreak is defined as a positive laboratory-confirmed test by a resident or a member of staff.