Measles in Ontario: Enhanced Epidemiological Summaries

This report is updated weekly and describes measles cases in Ontario, with a focus on the current outbreak. Case information is provided by age, sex, geography, severity, source of infection and immunization status.

Interpretation Notes
The data for this report are based on information entered in Ontario’s integrated Public Health Information System (iPHIS) as of the date and time noted in each report. iPHIS is a dynamic disease reporting system and data may be updated over time. Therefore, this report reflects a snapshot at the time of extraction and may differ from earlier or later reports.

As of January 1, 2025, nine local public health units voluntarily merged into four new entities. Since then, epidemiological reports present data from these merged public health units, based on combined case counts from the former public health units.