In the wake of a measles outbreak in Canada that has infected thousands of people over the past year, an international health agency revoked the country’s measles-free status on Nov. 10, 2025.

The Pan American Health Organization, which serves as the World Health Organization’s regional office for the Americas, made this announcement after the agency’s measles elimination commission met in Mexico City to review the latest public health data.

As a global health epidemiologist who studies the spread of infectious diseases, this change in status does not surprise me. Measles is highly contagious, and a drop in childhood vaccination rates in Canada and in other countries has left many children unprotected from the disease.

The resurgence of measles in Canada after decades with ver

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