Sep 26th, 2025

New report on HIV diagnoses in Ontario in 2023 and key findings from the HIV Look Back Project

Version française

The Ontario HIV Epidemiology and Surveillance Initiative (OHESI) is pleased to announce a new report: HIV diagnoses in Ontario, 2023. Understanding first-time HIV diagnoses is crucial to informing policy and action, including HIV prevention, treatment and care services. The focus of this report is on the proportions of key characteristics of first-time HIV diagnoses in 2023, with comparison to trends over the past 10 years. It includes analyses by age, sex, HIV exposure category, race/ethnicity, and geography. The report, “HIV diagnoses in Ontario, 2023,” reflects feedback from OHESI stakeholders and community members who have requested more concise reports.

This blog post aims to briefly summarize the findings of the report mentioned above.

OHESI classifies new HIV infections as either First-time HIV diagnoses (people with a first time positive HIV test in Ontario that do not report having had a previous positive HIV test outside of Ontario) and people with previous evidence of HIV (people who already knew their positive HIV status [within or outside of Ontario] at the time of their first positive diagnostic HIV test in Ontario).

Ontario completed a large HIV data quality project to better understand the numbers and proportions of first-time HIV diagnoses in 2023.

The HIV Look Back project was initiated to help better understand an increase in first-time diagnoses noticed in 2023 (compared to 2022) and to improve missingness in data.

In 2024, OHESI partner Public Health Ontario worked with 13 public health units to supplement missing laboratory data for key characteristics of first-time diagnoses in 2023.

There was no impact on the distribution of key characteristics for first-time HIV diagnoses in 2023, except for sex, which changed by 5%.

The other characteristics, age, health region, exposure, race/ethnicity, and sex remained the same.

The data supplemented from the HIV Look Back project is only used to show the change in the number of first-time HIV diagnoses and data stratified by sex in 2023. For all other analyses, data from the original numbers (i.e. 938) of first-time diagnoses are used (i.e., does not include data collected through the HIV Look Back project) to permit comparisons of trends in proportions over time. Overall, the HIV Look Back Project findings provide reassurance in the interpretation of data presented for first time HIV diagnoses in 2023.

Key findings from the 2023 HIV Diagnoses Report

There were 938 first-time HIV diagnoses in 2023. After the HIV Look Back Project, with additional information on previous test history, the number of first-time diagnoses in Ontario in 2023 decreased to 723 (a 23% decrease).

In 2023, OHESI data showed that there were 938 first-time HIV diagnoses and 551 people with previous evidence of HIV. 938 was an increase that exceeded historical trends. This prompted the HIV Look Back project. After incorporating information from the HIV Look Back Project, the number of first-time diagnoses decrease to 723 and the number of diagnoses with previous evidence of HIV increased to 766.
See the complete figures

Males represent the highest proportion of first-time HIV diagnosis compared to females.

The proportion of males was 75.3% (n=543) after the Look Back Project. Between 2014 and 2023, males accounted for a greater proportion (n=658 for males and n=276 for females) of first-time HIV diagnoses compared to females. However, the proportion in females (n=276) has slightly increased. The proportion of females was 24.7% (n=178) after the Look Back Project.

The majority of males indicated male-to-male sexual contact as their exposure category while most women indicated heterosexual.

See the complete figures

Toronto represents the highest proportion of first-time HIV diagnosis by health region, followed by Central East and Central West.

Toronto accounted for the highest proportion of first-time HIV diagnoses, although this number has been decreasing since 2019. Northern, South West and Eastern regions have remained relatively stable. Central East and West have both increased in proportion of new diagnoses since 2019.
See the complete figures

People who reported their race/ethnicity as Black accounted for the largest proportion of first time HIV diagnoses in Ontario followed by White, Latino/a/e/x and South Asian.

People who reported their race/ethnicity category as Black accounted for the largest proportion of first-time HIV diagnoses. Between 2019 an 2023 the proportion of first-time diagnoses decreased in people who reported their race/ethnicity category as white. First-time diagnoses slightly increased for those who reported their race/ethnicity as Latino/a/e/x and South Asian.
See the complete figure

The proportion of first-time diagnoses reporting heterosexual exposure is increasing.

Between 2019 and 2023, the male-to-male sexual contact exposure category has consistently represented the greatest proportion of first-time HIV diagnoses; however, there has been a slight decrease over time. Over the same period, the proportion of first-time HIV diagnoses reporting a heterosexual contact exposure category (i.e. for heterosexual contact, identified risk, and heterosexual contact, no identified risk) has been gradually increasing.
See the complete figures

It is important to note that there are multiple factors that influence year-to-year changes in HIV diagnoses including population-level, health system, patient/client, physician/clinician factors, and surveillance methods.

FactorsExamples
Population-level• Changes in migration from other provinces/territories or countries
• Changes to HIV transmission patterns within Ontario
Health system• Access to HIV testing (decreased during the COVID-19 pandemic)
• Lack of culturally safe care
• Focused key population testing campaign
Patient/client• Access to HIV Pre-Exposure Prophylaxis (PrEP) and Post-Exposure Prophylaxis (PEP) for at-risk populations
• Changes in drug use and sexual behaviours (e.g., decreased sexual activity during the COVID-19 pandemic, mpox outbreak)
Physician/ clinician• Changes in HIV testing practices (e.g., awareness of 2023 HIV testing guidelines)
Surveillance methods• Changes to data collection and integration (e.g., HIV Look Back Project)
Please read the full report – download here

The Ontario HIV Epidemiology and Surveillance Initiative (OHESI) is a collaborative partnership involving the Ministry of Health (MOH), Public Health Ontario (PHO), the Public Health Agency of Canada (PHAC), and the Ontario HIV Treatment Network (OHTN).