Measles cases continue to grow in Ontario, where 1,834 people have been infected since the beginning of January alone.
Most of those cases are connected with a multi-jurisdictional outbreak that began last fall in New Brunswick and has spread through communities in Ontario since then. Other cases, including two in Ottawa earlier this month, are travel-related.
An additional 173 cases have been identified since the last update from Public Health Ontario one week ago. The majority of outbreak cases are among infants, children and adolescents who were unimmunized.
Communities in southwestern Ontario have been the epicentre of the outbreak, but there are also cases in eastern and north-central Ontario.
The growing Ontario measles outbreak has caused New York State to issue travel warnings to residents. Public health officials in Ontario are also warning residents to take additional steps – including vaccinating infants as early as six months instead of waiting for one year – when travelling overseas or to parts of southwestern Ontario considered high risk.
Ontario’s measles outbreak is expected to continue into the summer. It is by far the largest in decades.
Between 2013 and 2023, for example, there were 101 confirmed measles cases reported in Ontario. In 2024, there were a total of 64 cases. Less than half way into 2025, Ontario has seen 28 times as many cases as it did last year.
Measles is high infectious and can cause serious complications. Ninety per cent of people who are unvaccinated or have never had measles will become infected if exposed to measles, which spreads through the air for up to two hours after an infected person has left the room.
For more information:
ottawapublichealth.ca/en/professionals-and-partners/hcp-measles.aspx
