Dramatic measles outbreaks worry health officials

There have been 95 measles cases reported in Canada so far this year — with Quebec, Ontario and Manitoba reporting new cases in the last week, says Canada's chief public health officer. 

That's in contrast to 147 cases for all of last year. 

"The fact that … the numbers are growing this year demonstrates how this virus can spread if people were not vaccinated," Dr. Theresa Tam told CBC News on Tuesday. 

"What I would like to see is that we stop these outbreaks in their tracks so that it doesn't become entrenched in the Canadian context."

The most recent data from the Public Health Agency of Canada (PHAC) shows 34 new cases in the week of Feb 8, but that figure is already out of date because Ontario's outbreaks have grown. 

Tam says an outbreak that now spans several provinces began in October in New Brunswick.

The first person known to be infected in southwestern Ontario's Grand Erie Public Health region travelled to New Brunswick to attend a wedding, says the region's acting medical officer of health, Dr. Malcolm Lock.

"It's my understanding that a traveller infected with measles [from Europe] attended that wedding," Lock said. "Because of that, the disease was transmitted to a number of the people that were there, who in turn have now returned to their own communities, and if those communities are under-immunized then it's just a cascade."

The resulting outbreak in Brantford, Ont., and the surrounding counties is moving fast, Lock said, given that it started before Christmas and seemingly hasn't yet peaked. 

Measles is a highly contagious virus that's most dangerous to children under age five. 

The virus spreads easily through the air and can cause a hacking cough, high fever and a red, blotchy rash.

Measles can lead to high hospitalization rates. What's more, it is estimated nearly one to three of every 1,000 children who become infected will die from respiratory and neurological complications, such as pneumonia and brain damage. 

Speaking generally, Lock says measles can lead to "nasty complications, particularly in children of upper respiratory problems, pneumonia and in some cases meningitis and encephalitis." The problems can persist throughout life. 

Dr. Sarah Wilson, a public health physician with Public Health Ontario in Toronto, says the province expects to add 50 to 60 new cases in its update later this week. It is Ontario's largest outbreak in more than a quarter century.  

"I wasn't expecting in my career to have to be responding and supporting to a measles outbreak such as this," Wilson said. "It is very dramatic to see the large number of cases and to see how quickly they're accumulating. But… I am also reassured that we do have a control strategy for measles and that's vaccination."

Manitoba health officials have confirmed five cases there connected to an outbreak in Ontario. 

Measles doesn't have a specific treatment. 

For prevention, two doses of the measles vaccine are considered enough for full protection in both adults and children. The first dose is usually given to babies at 12 to 15 months, and the second before the child starts school.

While measles was eliminated in Canada in 1998 through widespread vaccination, cases still occur sporadically. Between 1998 and 2024, there's been an average of 91 cases reported each year, most acquired by travel outside the country.

Most cases reported in Canada occur among unvaccinated people, many of whom are children, including infants under one who have not yet had the opportunity to be vaccinated, says PHAC.

Vaccine uptake declines

Since December, Quebec has also been experiencing measles. The province's latest outbreak includes 28 cases, with the Laurentians area north of Montreal hardest hit with 21. 

Dr. Éric Goyer, director of public health in the Laurentians, says the virus was also introduced to that region from abroad.

Goyer says his agency is encouraging children and students to be fully vaccinated. Staff are also working to ensure those who are not adequately vaccinated stay out of school until the outbreak ends. 

Tam says the outbreak in the Laurentians began at a conference in Montreal.

In 2024, a study published in the Canadian Journal of Public Health found that there was a decline in measles vaccination in children in 2023 compared with 2019.

The outbreaks are "likely related to poor vaccine uptake more than anything else," said Dr. Earl Rubin, director of the infectious diseases division at the Montreal Children's Hospital.

Dr. Jia Hu, a public health physician and interim medical lead for immunization programs at the B.C. Centre for Disease Control's vaccine preventable disease service, says for something as contagious as measles, vaccine uptake needs to be as high as possible. 

B.C.'s two cases of measles in 2025 have both been travel related, Hu says.

Public health officials are encouraging people to make sure their immunizations are up to date ahead of any travel this spring, given that measles outbreaks are also underway in Texas, along with tens of thousands of cases in Europe, and in Asia and Africa.