Ontario's 993 Measles Cases Outpace the United States

A multijurisdictional measles outbreak is ongoing in Canada and the United States in 2025.

Although measles was eliminated in Canada in 1998, an average of 91 cases, many travel-related, were reported annually.

According to the Canadian Government's data release on May 2, 2025, the current outbreak began in New Brunswick in October 2024 and has continued to spread in Alberta, Manitoba, Ontario, Prince Edward Island, and Quebec.

The data revealed 970 measles cases had been reported in Ontario, out of the 1,177 total cases in Canada. Of the virus genotypes analyzed, D8 was dominant.

During Ontario's outbreak, 451 measles cases have been confirmed in Ontario's Southwestern Public Health, including the City of St. Thomas, Elgin County, and Oxford County.

Data from Toronto, a city with over 2.7 million people, has confirmed only three cases.

These data indicate that Ontario's measles outbreak is primarily a rural, not urban, concern.

As of May 1, 2025, the Centers for Disease Control and Prevention (CDC) reported 935 confirmed measles cases in 30 U.S. jurisdictions, with Texas the leader.

Measles is an exceptionally infectious virus but can be easily prevented with an effective vaccine.

A study published by The Lancet in May 2025 supports using the MR vaccine at six months to protect young infants during measles outbreaks and in settings with increased risk or high transmission.

The CDC recommends evaluating your family's need for early vaccine doses before international travel. After you return, monitor your health for three weeks and call your healthcare provider if you or your child gets sick with a rash and fever.