Design: Descriptive cohort from public health surveillance
Population: 2,377 confirmed or probable measles cases in Ontario
Primary outcome: Demographics, vaccination status, complications, international spread
Effect: 89% unvaccinated; 7% hospitalised; 10 congenital infections; 1 infant death

A BMJ descriptive cohort, published on 28 October 2026, set out the Ontario measles outbreak that ran from late October 2024 to early October 2025 and contributed to Canada losing its elimination status. There were 2,377 cases, 90% within historically under-vaccinated communities, 73% in people aged 19 or under, and 89% unvaccinated.

About 7% were admitted to hospital and 13 to intensive care. There were 51 infections in pregnancy, 10 congenital infections, one case of encephalitis and one infant death. Sequencing identified a new strain, later found in the United States, Mexico and the Netherlands.

The outbreak stayed largely within under-vaccinated groups, which the authors attribute to high immunity elsewhere. The lesson for any country is that elimination depends on closing local immunity gaps, and that clinicians should think of measles in a febrile rash again.

Think of measles in anyone with fever, rash and cough, coryza or conjunctivitis, especially if unvaccinated or recently travelled.
Isolate a suspected case promptly and notify public health before confirmation.
Check MMR status at every child contact and in adults born after vaccination began.
Measles in pregnancy carries risks to mother and baby; ask about immunity in antenatal care.

Why it matters

Elimination status can be lost within a year where immunity gaps cluster, and clinicians are the first to see it.

The statistics, in plain English

This is a descriptive count, not a comparison, so it shows who was affected rather than measuring risk. Hospital admission in about 1 in 14 cases gives a sense of the burden.