Canada Could Lose Measles Elimination Status If Outbreak Persists Into Fall, Health Advisor Warns

On Thursday, as Public Health Ontario added 197 infections to its weekly count, a senior medical advisor with the Public Health Agency of Canada said out loud what officials had been reluctant to say: Canada could lose its measles elimination status. Dr. Marina Salvadori, speaking from Toronto, said that would happen only if the disease keeps spreading past mid-October 2025.

The term has a precise meaning. Elimination is the absence of continuous transmission of measles for twelve months or more in a given geographic area. Canada reached that status in 1998. An outbreak that stays alive into the fall would break that streak.

Salvadori was careful about what losing the status would and would not mean. She said people hear the phrase and fear that measles will re-establish itself and become common, exposing everyone for decades to come. It does not have to go that way, she said. Even if the status is lost, she said she believes Canada can eliminate measles again.

The Ontario numbers show the scale of the problem. The province's tally of probable and confirmed cases stands at 1,440 since the outbreak began in October. Of those, 101 people have been hospitalized, 75 of them children, and eight patients have been in intensive care. Dr. Sarah Wilson, a public health physician at Public Health Ontario, noted that hospitalizations amount to seven per cent of the province's outbreak cases. To her, she said, that is a clear sign that measles can bring severe complications and is not a trivial infection.

The outbreak reaches well beyond Ontario. Alberta reported Thursday that its total had reached 313 cases since mid-March, including 19 hospitalizations. Saskatchewan updated its cumulative count to 27. On Wednesday, Manitoba reported 24 cases. Nova Scotia and the Northwest Territories each reported cases earlier this week, their first since this outbreak began.

In Regina, Saskatchewan's Chief Medical Health Officer, Dr. Saqib Shahab, told a news conference that he expects new cases every day going forward. He described the province as now part of an unprecedented North American measles outbreak. His language was pointed: measles should not be appearing in 2025, he said, and outbreaks in specific communities that look like the 1950s mean the social contract of keeping each other safe and protected has been broken.

The outbreak is also a continental one. Salvadori said Canadian officials have been meeting with the United States' Centers for Disease Control and Prevention and with public health colleagues in Mexico, since all three countries have been struck. They are comparing what the cases have in common. She said everyone is dealing with the same thing and working well together to gain insights and understand what is going on.

What to watch is the calendar. Mid-October is the line Salvadori named, and the weekly case counts from Ontario, Alberta, Saskatchewan and Manitoba will show whether transmission is slowing or still running as that date approaches.