Vancouver Coastal Health says it's facing an "outbreak" of measles with nine cases in the city this month.
The number of confirmed cases more than doubled from four earlier on Friday, when the health authority said all the infections involved three French schools.
Two of the schools are connected by a door and the schools use the same bus company.
Medical health officer Dr. Althea Hayden says most of the new confirmed cases are linked to one of the French schools.
She says eight cases were confirmed this week and another unrelated case was confirmed last week, bringing the total to nine this month.
Hayden says many of the people exposed have already been vaccinated, but she's asking anyone who may be at risk to get checked out.
British Columbia's health minister has urged people to get vaccinated to protect themselves from the highly infectious disease.
Adrian Dix says it's the responsibility of parents to ensure their children are vaccinated and to also think of other people's kids who could be infected.
He says vaccination rates could be higher and anyone who needs more information should contact their local health authority.