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Ontario measles cases nearly double count marking largest increase in almost 30 years

TORONTO — 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.
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A sign is seen outside a clinic with the South Plains Public Health District Sunday, Feb. 23, 2025, in Brownfield, Texas. (AP Photo/Julio Cortez)

TORONTO — 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.

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.

Across the country, Public Health Agency of Canada is reporting 77 cases this year, but its latest data is outdated and only spans to Feb. 8.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.

This report by The Canadian Press was first published Feb. 27, 2025.

Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.

Hannah Alberga, The Canadian Press

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