Technical Notes: Health regions

Individuals who receive an HIV diagnostic test are assigned to a geographic region based on their residence or, if not reported, the address of the ordering provider. Approximately 28% of diagnoses are missing information on address of residence in 2019 and assigned based on provider address.

Ontario can be divided geographically by health region or public health units (PHU). These are defined below:

• Health regions – Groupings of PHUs that have historically been used in HIV epidemiology and surveillance reports. See the following page for health region breakdowns.
• Public health unit – A health agency that provides health promotion and disease prevention programs. There are currently (2021) 34 PHUs in Ontario and each has its own unique geographical boundary. This is different from previous years where there were 36 PHUs (2017 and before). The change reflects the Oxford PHU being combined with the Elgin-St. Thomas PHU to form the new ‘Southwestern’ PHU. It also reflects Huron and Perth being combined. The larger health regions did not change from previous reports.

Groupings of public health units for each health region:

Figure i: Geographic map of health region and public health unit boundaries. Map created using Statistics Canada boundary files