Measles outbreak shows no signs of slowing down in Ontario

Measles outbreak shows no signs of slowing down in Ontario.

This story was updated on March 19, 2025 after Public Health Ontario adjusted their reporting data. — Measles cases continue to climb across southwestern Ontario.

According to a new report from Public Health Ontario, 252 confirmed infections and 66 probable cases have been reported across 11 health units in just the three months of 2025.

More than half of those illnesses are within the coverage area of Southwestern Public Health and Grand Erie Public Health.

The data showed 181 measles cases were reported by Southwestern Public Health.

Grand Erie Public Health, in a media briefing Thursday, said that as of March 13, there were aware of 110 measles cases. Of those, 21 were in adults, 70 in children and the remaining were probable infections.

All but three of those cases were in Norfolk County.

New data from Public Health Ontario

The Measles Epidemiological Summary Report, put together by Public Health Ontario, showed a sudden spike in measles cases over the last year.

Between 2013 and 2023, there were 101 confirmed cases of the virus and a total 64 illnesses in 2024. As of March 12, there were 350 cases in 2025.

“The sharp increase in the number of outbreak cases and the geographic spread in recent weeks is attributable to ongoing exposures and transmission among individuals who are unvaccinated,” the report said.

The data showed 297 had no previous measles vaccine and one person had one dose. Twelve had two doses and were considered fully vaccinated. The remaining 40 cases had an unknown vaccination status.

Public Health Ontario said 93.8 per cent of the children who contracted measles were unimmunized, while 60.9 per cent of adults reported the same.

Among the outbreak cases, 31 people required hospitalization for measles complications. The agency said 27 were unimmunized children, one of whom ended up in intensive care.

Mitigating the spread

Experts warn that measles is a high-contagious disease.

“A medical mask is not sufficient to fully protect against the virus,” Dr. Ninh Tran, the medical officer of health for Southwestern Public Health, said during Thursday’s briefing.

Measles can survive in the air, or on surfaces, for up to two hours after an infected person leaves the area.

The most common symptoms are a red blotchy rash on the body, fever, runny nose, cough and red, watery eyes.

Other symptoms may not immediately seem related to measles, such as ear infections, diarrhea, respiratory issues and encephalitis. More serious complications can include pneumonia and brain infections.

“There are signs and symptoms of measles that can be mistaken for something else, until you have the rash,” said Tran. “That’s usually the telltale sign, but not everyone has that.”

Experts advise anyone who believes they may have come in contact with an infected person, or visited a location where they may have been exposed to the virus, to immediately contact their doctor or healthcare provider.

“Even if you are masked or have been exposed to the measles and are not vaccinated, you can still become infected,” Tran said. “Please avoid healthcare settings, including hospitals, unless you require medical care for worsening or severe symptoms. If you do require this care, do not delay seeking support from a medical professional. But it is really important to call ahead to inform them of your symptoms so they can better prepare for your arrival and take appropriate precautions to prevent others from getting sick too.”

Officials said there’s only one reliable way to stop the illnesses spread.

“Measles is a vaccine-preventable infectious disease,” Tran explained. “The vaccine is your and your family’s best line of defense against this highly contagious virus.”

Grand Erie Public Health said the vaccination goal for herd immunity is 95 per cent. That, they added, would “really help to mitigate the spread of isolated outbreak.”

Update from Huron Perth Public Health

Huron Perth Public Health, which covers Stratford and surrounding areas, said there have been 16 reported cases of the measles as of March 13. Nine of those are confirmed, while the remaining six are probable cases.

The health unit did not provide any further breakdown, if those cases were in adults or children, or if anyone had been hospitalized.

Officials did confirm a link to the existing outbreaks in nearby communities.

“Initial cases were connected to the ongoing outbreak in the Southwestern Public Health and Grand Erie Public Health regions,” they said in an email to CTV News. “Since measles is extremely contagious for unvaccinated people, there has also been some community spread within Huron Perth among under vaccinated communities.”

Other communities

Warnings about the spread of measles have also been issued in many other communities across Ontario.

On Thursday, the South East Health Unit reported 32 measles cases in Hastings County, near Kingston.

Health alerts have also been issued in Woodstock, Tillsonburg, Hamilton, London and Toronto.

Visitor restrictions are also currently in place at Windsor Regional Hospital due to the increase in measles cases. Starting Thursday, children under the age of 16 are not permitted inside the hospital unless they are receiving medical treatment.

Measles outbreaks have also been reported in Alberta and Quebec, while Europe is seeing its highest number of cases in 25 years.

“Following a backsliding in immunization coverage during the COVID-19 pandemic, cases rose significantly again in 2023 and 2024,” the World Health Organization said in a statement. “Vaccination rates in many countries are yet to return to pre-pandemic levels.”

- With files from Reuters