Measles cases nearly double in Ontario over last 2 weeks, far surpassing last decade's total
18 unimmunized children hospitalized as a result of recent outbreak
Ontario identified 78 new measles cases over the course of two weeks, public health officials said Thursday, calling it the largest outbreak the province has seen in almost 30 years.
The new cases bring Ontario's total this year to just over 140, far surpassing the 101 total infections recorded in the province between 2013 and 2023.
Dr. Sarah Wilson, a public health physician with Public Health Ontario, said the last time there was a sizable outbreak in the province was 2008 when there was a total of 58 cases.
"This is the largest measles outbreak that we've experienced in the province of Ontario since measles was eliminated from Canada in 1998," Wilson said.
Almost all of the new cases are connected to an interprovincial outbreak that began in October, which has sickened
177 people in Ontario and also saw the virus spread in New Brunswick and Manitoba.
The epicentre of Ontario's outbreak has been in neighbouring Southwestern and Grand Erie public health regions. Wilson said the concentration of cases in unvaccinated people could explain how quickly the outbreak spread over the last two weeks. Quebec has also reported an outbreak of 27 cases that began in December.
As a result of the outbreak, 18 kids have been hospitalized in Ontario, including one who required intensive care.
Province usually sees 0 to 22 cases a year: physician
Dr. Christine Navarro, another public health physician at Public Health Ontario, said until this outbreak, most cases were related to travel.
Navarro said New Brunswick's outbreak, which began with an exposure there and spread to Ontario, was declared over in January.
"In Ontario, we continue to have transmission and this is as a result of the introduction of the measles virus to communities where the immunization rates are low," Navarro said.
Navarro said it's difficult to say if the outbreak has reached a peak or not.
"We have had a quite a significant increase from our last epidemiological report that was two weeks ago," she said.
"However, we hope that with continuing efforts of investigation, providing vaccination testing as well as contact management, letting people know about signs and symptoms and where they can seek care, we hope that will help to stem the tide of this outbreak."
Navarro said the number of cases is the largest that Ontario has had in the years between 2013 and 2023. She said the province typically has between zero and 22 cases a year.
Dr. Sarah Khan, an associate professor in the pediatrics department at McMaster University, said on Thursday that people are at risk because vaccination rates have gone down and it's important that people keep their immunization records up to date.
"It's probably good we all just know our status because if you get that call from public health, they're going to ask you: 'Are you sure you're immune?' And you're going have to provide that proof. And so, I think it's just better we all kind of check that and get caught up."
Khan said prevention is key to stopping the spread of measles and prevention means vaccination. She said if there is a community that is "entirely non-immune," it will spread rapidly within that community.
"That said, with contact tracing, post exposure prophylaxis, risk mitigation, isolation, all of these measures, we typically can get things back down."
Khan said there needs to be education, awareness and efforts to improve the reputation of the Mumps, Measles and Rubella vaccine because it's a very safe vaccine.
"Anyone that has questions about it should really talk to their healthcare provider. Because I can tell you from experience, measles is a very severe disease, can result in severe conditions that result in hospitalization, ICU admission. And we've had deaths in in our community."
The highly contagious — but preventable — airborne disease has primarily infected children and teenagers who are unvaccinated.
One of the cases reported Thursday was in an unvaccinated child who acquired measles outside of Canada and required hospitalization.
Canada 'at risk' of losing elimination status
Across the country, Public Health Agency of Canada is reporting 77 cases this year, but its latest data is outdated and only spans to Feb. 8.
The U.S. is also seeing measles spreading, marking its first measles death in a decade Wednesday after an unvaccinated child died in Texas.
Measles is one of the most contagious diseases in the world. Each patient with measles can transmit the virus to another 16 to 18 people, said Janna Shapiro, a post-doctoral fellow at the Centre for Vaccine Preventable Diseases affiliated with the University of Toronto.
For that reason, it usually serves as a sign of what's to come.
"Whenever vaccination rates start to go down, we get worried about measles because it's the first thing that's going to come back because it's so, so, so contagious. That is also what allows these outbreaks to grow faster than other types of outbreaks," Shapiro said.
It usually begins with a fever, cough, runny nose and red watery eyes, followed by a red blotchy rash that starts on the face and spreads to the body and limbs. The virus can lead to pneumonia, inflammation of the brain and death.
Canada eliminated measles in 1998, which required a low level of transmission for at least a year and 90 to 95 per cent vaccination coverage.
"We're now at risk of losing our elimination status in Canada if these outbreaks continue," Shapiro said.
With March Break around the corner, she said airports and planes are opportune places for the virus to spread, and vaccination is the best path of protection.
"There's a misconception for some people that measles is not a serious disease. And measles very much is a serious disease," Shapiro said.
Corrections
- An earlier version of this story by The Canadian Press said there were 84 new measles cases reported in Ontario over the last two weeks. In fact, there were 78 new cases.Feb 27, 2025 4:46 PM EST
With files from CBC News