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 École Jules-Verne, a French-language high school in South Vancouver, reported CBC News.
"We now have an outbreak," said Hayden. "Cases are occurring in staff, students and family members affiliated with this school."
Urging people to get vaccinated
She defined an "outbreak" as a number of cases that are higher than expected; Vancouver should have zero cases if immunization levels were adequate, she said.
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.
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She says eight cases were confirmed this week and another unrelated case was confirmed last week, bringing the total to nine this month.
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.
This comes after a measles outbreak that began last month in neighbouring Washington state. Officials say 47 of the 53 confirmed cases are people who were not immunized against the highly contagious virus.
Measles is spreads through the air, or through sharing food, drinks, cigarettes, or kissing an infected person.
Symptoms include fever, cough, runny nose, and red eyes, followed a few days later by a rash that starts on the face and spreads to the chest. Complications can include pneumonia, brain inflammation, seizures, deafness, brain damage, and death.
Someone can spread measles before knowing they have been infected. People are infectious to others from four days before to four days after a rash appears.