Ontario sees sharpest rise in measles yet with 223 new infections since last week

A sign outside Southwestern Public Health in St. Thomas, Ont. on Tuesday, March 4, 2025 warns residents to call ahead before visiting a doctor or hospital if they think they have the measles. THE CANADIAN PRESS/ Geoff Robins

TORONTO — Ontario is reporting its highest increase in measles cases since its outbreak began, with 223 new infections in the province over the past week.

That brings the total number of people in the province who have fallen ill from the virus to 1,243 since October. 

Public Health Ontario said in a report today that 84 people have been hospitalized – including 63 children – during the course of this outbreak. Eight patients have been admitted to intensive care.

The agency notes that its southwestern public health unit has had 57 new infections, compared to 15 the previous week. Neighbouring Grand Erie Public Health is also seeing an uptick with 46 cases, compared to two the previous week.

Southwestern Public Health Unit’s Dr. Ninh Tran said this “sharp rise” is due to exposures in large unvaccinated households between siblings and other family members, and places where unimmunized people gather.

He said the increase in cases is not tied to any “particular singular” event, but rather, it’s due to a group of cases linked to one another. However, he did not pin the spread to a particular group.

Tran said the duration of hospital stays on average is usually just over three days, and ranges from about one to 11 days. 

Alberta reported 170 measles cases Wednesday – including nine hospitalizations – since its outbreak began in March.

Alberta Medical Association president Dr. Shelley Duggan told The Canadian Press last week the numbers suggest that within weeks, that count could skyrocket to more than 1,000, like in Ontario.

This report by The Canadian Press was first published May 1, 2025.

Hannah Alberga, The Canadian Press