Measles in Canada: What to know

As outbreaks of measles continue to pop up throughout Canada, Europe and the U.S. there are signs vaccination rates have fallen below what is necessary to keep the disease at bay.

“If one person who’s infected is exposed to 10 people who are not infected, probably nine of those 10 people will get the infection, (assuming they are not vaccinated,)” said Jacqueline Khet-ling Wong, staff physician and assistant professor in the Department of Pediatrics, Division of Infectious Diseases, at Mcmaster University. “The groups where we normally see complications would be children, pregnant women and the immunocompromised, but, worldwide, in terms of the number of infections, hospitalizations, complications and even deaths ... is borne by children.”

Measles, although having been officially eliminated in Canada, is one of the world’s most contagious diseases.

On Friday, according to Montreal health officials, a case of measles in Laval shows signs that it may be active in the community, as an unvaccinated person contracted the virus without leaving the country and without interacting with another known host.

Quebec public health officials on Monday said the Montreal area has become the epicentre of measles cases in Canada.

This comes just as March break begins in Quebec and New Brunswick and, at most, a few weeks before it begins in other provinces. March break, and international travel as a whole, could be a significant catalyst in the spread of measles in unprotected pockets of the Canadian population, according to Chief Public Health Officer Theresa Tam. Tam urged those who are currently not fully vaccinated against the virus to get their two doses, especially before any international travel.

“You’re just a flight away sometimes in terms of exposure to infections in other parts of the world,” Wong said.

As of Feb. 23, health officials were aware of six cases of measles in Canada since the beginning of the year, but with the string of recent cases in Montreal, that number could rise. In 2023, there was a total of 12 known cases of measles throughout the entire year.

The first known case of measles this year was an infant in Toronto who is believed to have contracted the virus after international travel. However, another case in York Region, Ont., saw a fully vaccinated 30-year-old man become infected with a mild form of the disease.

Unlike the three other cases of measles in Ontario before that point, he had contracted the virus without travelling or interacting with anyone known to be carrying the virus.

Since COVID-19, surveys have shown that Canada has a small minority of people who are increasingly vaccine hesitant or against vaccination for their children.