Canada achieved measles elimination status in 1998. Now, it could lose it

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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.

Now, the region is at risk of losing that status again, if Canada's outbreak isn't contained in the coming months.

"We're hoping that Canada is going to stop the outbreaks and they're going to maintain the verification, but this is something uncertain," said Dr. Daniel Salas, executive manager for the Comprehensive Special Program on Immunization at PAHO in Washington, D.C.

While Salas said the status itself is symbolic, losing it represents an increased risk across the region.

"What we are more concerned about is all those disruptions of burden of disease, the mortality that measles can cause and, unfortunately, the situations of fragility," he said. That includes people living in poverty, without access to timely health-care services and children suffering from malnutrition who can be more susceptible to complications or death.

Worldwide, more than 100,000 people — mostly children under the age of five — died from measles in 2023, according to the World Health Organization (WHO). That same year, 22 million infants missed at least one dose of the measles vaccine.

The WHO estimates vaccines prevented around 60 million deaths between 2000 and 2023.

Canada last went through the verification process in November of 2024, according to infectious diseases specialist Marina Salvadori, a senior medical advisor at the Public Health Agency of Canada, and is now preparing for the next one. It will look at a range of elements including the number of cases Canada has, the country's laboratory standards and immunization rates.

With just five months left before that crucial one-year mark, Salvadori said she wouldn't be surprised if the outbreak continues past October.

Still, even if Canada loses elimination status, Salvadori is confident the country could regain it through continued vaccination pushes.

Because measles is one of the most contagious viruses humans can catch, 95 per cent of the population needs to be immunized to reach herd immunity, meaning the population is considered well-protected.

Canada's vaccination rate is below that threshold. First-dose coverage declined between 2019 and 2023, from 90 to 83 per cent, according to the Public Health Agency of Canada.

"What I really don't want to see is true endemicity, where children are at risk and where this is a normal childhood infection. Because there's nothing normal about measles. It's a serious, serious infection," Salvadori said.

Measles can have dangerous consequences, especially for children, she said, including pneumonia, swelling of the brain and even death.

Cases are primarily spreading among people who are unvaccinated or under-vaccinated. In Ontario, for example, nearly 90 per cent of the cases are among those who are not immunized. Public Health Ontario's Dr. Wilson said that makes stopping the virus difficult.

In Manitoba, which is also experiencing an outbreak, provincial health officials have expanded vaccine eligibility in the most affected regions, offering shots to children aged six months to one year, in addition to the routine schedule that starts at 12 months.

Dr. Lee, in Winnipeg, said there is still time for people hesitant about vaccines to reconsider.

"It's not a matter of saying 'you have to,' but having conversations and trying to understand why people are hesitant to take the vaccine," Lee said. "We need to meet people where they're at."