Ontario’s chief medical officer of health has announced that measles cases in the province have hit the highest level in over a decade.

“Over the last several weeks, we have seen the number of new measles cases rise to 173 bringing the total number of confirmed cases in Ontario to 350 since 2024, including 31 hospitalizations,” Dr. Kieran Moore said in a statement Friday.

“This is the most measles cases Ontario has seen in over a decade. It is critical we work together to mitigate further spread of this vaccine-preventable disease,” he added.

Over 96 per cent of Ontario’s cases are among individuals who are unimmunized, or have an unknown immunization status, and were exposed in their community or while travelling, according to Dr. Moore.

“Vaccination is the most effective way to limit the spread of measles and protect yourself and your loved ones. The measles, mumps and rubella (MMR) vaccine has been in use for more than 50 years and is proven to be one of the safest and most effective vaccines available,” Dr. Moore said.

Measles spreads “easily” among those who aren’t vaccinated and can lead to serious health issues including pneumonia, respiratory failure, swelling of the brain, and in rare cases, death, according to Dr. Moore.