Canada achieved measles elimination status in 1998. Now, it could lose it
CBC
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As Canada's measles outbreak continues to grow, the country is at risk of losing its measles elimination status — a bar set by the World Health Organization.
"The risk is substantial," said Dr. Sarah Wilson, a public health physician with Public Health Ontario who has been tracking the measles outbreak in that province.
Ontario is now reporting more measles cases each week than it once saw over an entire decade, Wilson said. "It is a very different situation than what we experienced in the last decade since measles elimination was achieved," she said.
Measles elimination is reached when a virus is no longer endemic — circulating regularly — in a certain country or region. It's different from eradication, which is when person-to-person transmission has been eliminated globally. A country can lose elimination status when transmission of the virus continues for one year or more.
Canada's outbreak began in October 2024. That means if sustained transmission continues until October 2025, the Pan American Health Organization (PAHO) can revoke the elimination status.
Canada currently has more cases than any other country in the Americas, according to PAHO.
Data from the Public Health Agency of Canada shows measles cases continue to spread to more provinces and territories.
The largest outbreak is in Ontario where there have been 1,795 cases since October, according to the latest numbers from Public Health Ontario. Alberta's outbreak is growing too, with more than 500 cases as of Friday.
While losing elimination status might not affect Canadians' day-to-day lives, Dr. Santina Lee, a pediatric infectious disease specialist in Winnipeg, said it would be an unfortunate marker.
"It would definitely feel like a bit of a step back," said Lee, given that measles is a vaccine-preventable disease.
"For an infection like measles where we do have the tools, and to not be able to use them to the full extent that they are available, I think definitely is a challenge."
PAHO is the body that verifies measles elimination status in the region, which is made up of 35 member states. The region as a whole was the first in the world to eliminate measles in 2016. It lost that status three years later, because of outbreaks in Venezuela and Brazil, but re-gained it in 2024. The U.K. and U.S. have also seen the return of transmission in recent years, with the U.S. coming close to losing its elimination status in 2019.
Brazil was able to end its outbreak thanks to targeted vaccine campaigns in priority communities, expanding molecular testing to identify the virus and training rapid response teams, according to PAHO.
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This story is part of CBC Health's Second Opinion, a weekly analysis of health and medical science news emailed to subscribers on Saturday mornings. If you haven't subscribed yet, you can do that by clicking here.