Measles spreading in Ontario, Quebec with cases of unknown origin

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Community transmission of measles may be occurring in at least two provinces, a development that could have significant public-health ramifications. Health officials in both Ontario and Quebec said this week they had confirmed cases with no links to international travel or people infected with the virus.

Quebec’s health director, Luc Boileau, said in a notice to health professionals Thursday he is concerned the virus is spreading in the community after officials identified a case of measles in an individual in Laval, a Montreal suburb, who does not know how the infection occurred.

Also on Thursday, health officials in York region, in the Greater Toronto Area, said they had identified a case in a male in his 30s with no known exposure.

Measles is no longer endemic in Canada, meaning the virus is typically introduced through international travel. The fact these individuals don’t know how they got sick “implies that there are additional cases of measles that haven’t been detected or diagnosed,” said Danny Chen, physician lead of infection prevention and control at Mackenzie Health, based in York region.

Last month, the country’s Chief Public Health Officer, Theresa Tam, issued a statement in advance of March break saying she is concerned that an uptick in measles cases around the world combined with lower vaccination rates in Canada could result in transmission of the virus in communities here.

The return of measles is cause for concern, not disdain

Nearly a dozen cases of measles have been confirmed in Canada so far this year, compared with 12 during all of 2023. Earlier this week, officials in Ontario’s Brant County confirmed a case of measles in a Brantford-area child who recently returned from Europe.

Information released by the Brant County Health Unit seems to indicate the child was taken directly to the Brantford General Hospital’s emergency department from Toronto’s Pearson International Airport on Feb. 23, followed early the next morning by a trip to the emergency department at McMaster Children’s Hospital in Hamilton. Anyone who was on the child’s flight from London’s Heathrow Airport, or in either emergency rooms at the same time, could have been exposed to the virus.

Hospitals typically have processes in place to isolate individuals who may be infected with measles or another communicable virus, Dr. Chen said. But it can be challenging to identify measles early on, as the virus’s trademark rash typically doesn’t appear until a few days after the onset of illness.

Fifth measles case in Canada this year has officials worried about outbreaks

Measles is one of the most contagious viruses in existence. Almost everyone who comes into contact with it will get sick as a result if they aren’t vaccinated or don’t have prior exposure. Complications can be severe. About one in five people will require hospital admission, Dr. Chen said, while one in 10 will develop a complicating infection, such as pneumonia. About one in 1,000 will experience encephalitis, a dangerous swelling of the brain that can lead to deafness, blindness or intellectual disability.

To keep the virus at bay in a community, 95 per cent of people need to have received two doses of the measles, mumps and rubella vaccine. While Canada doesn’t have a national vaccine registry, the data that are available point to significant declines in MMR vaccination rates since the pandemic.

For example, as of 2022, only 74 per cent of children in Alberta had received two doses of the MMR vaccine by age seven, a decrease from 80 per cent in 2019, according to a provincial database.

People who are pregnant, those with compromised immune systems, and children under 5, particularly babies, face heightened risks of complications.