Measles, a vaccine-preventable disease, is surging across Canada, alarming health officials as new cases pop up throughout the country, with cases piling up in Ontario.
Canada’s measles outbreak began in October after a travel-related case in New Brunswick sparked outbreaks there and in Ontario. New Brunswick declared its outbreak over in January, but the virus is still spreading in Ontario and elsewhere in Canada.
During spring break, experts like infectious disease specialist Brian Conway worry that unvaccinated Canadians travelling to areas with high measles rates, particularly in the southern United States, could spark a further spread in Canada in the coming weeks.
“It’s very contagious. So if there’s even one case out there and large numbers of people are exposed to it and they’re susceptible, they will definitely get infected,” Conway told Global News. “We certainly do need to be vigilant.”
As of March 18, the latest data from the Public Health Agency of Canada (PHAC) shows 369 reported cases in Canada at the national level since the beginning of the year.
But those numbers have since gone up as measles cases in Canada can change by the day or even by the hour, said Kerry Robinson, acting vice-president of PHAC’s infectious diseases and vaccination programs branch.
“There is at least one multi-jurisdictional outbreak that’s affecting four provinces, and that is quite active. So that means that numbers can change on a daily basis, sometimes on an hourly basis, because local public health gets different types of numbers confirmed throughout the day,” she said.
While the exact numbers keep changing, health officials do know that the current measles outbreak began among unvaccinated people.
Measles is one of the most contagious infectious diseases — more contagious than diseases like COVID-19, influenza and chickenpox. This high level of contagiousness is one reason why measles outbreaks can spread rapidly, particularly in areas with low vaccination rates.
This is how the virus seems to be spreading across Canada, with PHAC reporting that nearly 80 per cent of cases are in unvaccinated individuals.
The New Brunswick measles outbreak began in the fall of 2024 and was linked to a travel-related case reported on Oct. 24. Officially declared on Nov. 1, the outbreak resulted in a total of 50 cases of the highly infectious virus.
People who were exposed to measles at a gathering in New Brunswick later travelled to and from Ontario, triggering an outbreak among unvaccinated populations there, Robinson explained.
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“Then there was some travel between Manitoba individuals into the Ontario community that was experiencing the outbreak that resulted in cases in Manitoba,” she said.
“And then we’ve seen sort of around the March break time period was that we’ve seen individuals travel either from Ontario to Alberta or from Alberta to Ontario. And so then we’ve seen some cases appear in Ontario and Alberta as a result of that.”
Measles cases are now confirmed in British Columbia, Alberta, Saskatchewan, Manitoba, Ontario and Quebec.
Some cases are linked to the ongoing outbreak, while others, like those in British Columbia, are connected to international travel.
Christine Navarro, a public health physician at Public Health Ontario, said measles cases in Ontario have “really accelerated” over the past few weeks. She worries that following March break, even more cases could emerge in the coming days.
“We haven’t seen this level of spread, certainly not since before measles was eliminated in Canada in 1998.”
“One of the major concerns is the impact on people who are most vulnerable, and those include infants who are too young to be vaccinated, persons with immunocompromised, as well as pregnant persons who may have severe outcomes.”
The measles were declared eradicated in Canada in 1998 following an extensive immunization campaign.
However, in recent years, it has resurfaced due to a decline in vaccination rates, according to Health Canada. Most cases come from abroad, brought into the country by travellers who are not vaccinated or who are under-immunized.
Since the virus spreads before symptoms even show and stays contagious for a while, outbreaks can be tough to control once they start.
“It takes between seven and 21 days after an exposure to measles for cases or symptoms to start to appear,” Robinson said.
“If anyone is symptomatic, they should seek care, but call ahead to a health care provider or ER to make sure the appropriate precautions are in place.
“But do not delay seeking care, in particular for young children so they can really get the support that they need.”
Measles usually starts with a fever, cough, runny nose and red, watery eyes before a red rash appears and spreads from the face down.
Most people recover, but it can lead to serious complications, especially for young children and those with weakened immune systems. In some cases, it can cause pneumonia, brain inflammation or, in rare instances, death.
“The large majority of the cases we’re seeing in the outbreak at this time are really in unvaccinated populations and pockets of our populations,” Navarro said.
This is why public health experts are urging Canadians to get their measles vaccine, as it’s both safe and effective.
The measles vaccine is available in Canada as measles-mumps-rubella (MMR) or measles-mumps-rubella-varicella (MMRV) vaccine. It’s estimated to be 85 to 95 per cent effective after a single dose given at 12 or 15 months of age. With a second dose, efficacy rises to nearly 100 per cent, according to PHAC.
For more details on who can get the vaccine and whether you’re up to date on your doses, click here.
— with files from Global News’ Katherine Ward
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