Ontario team finds increasing rates of key sexually transmitted and blood-borne infections (STBBIs)

Ontario researchers studied testing trends for sexually transmitted and bloodborne infections
Cases of two infections diagnosed at the same time increased 10% per year from 2013 to 2023
These co-infections were most common in Northwestern Ontario, followed by the Toronto area

Researchers at McMaster University in Hamilton and Public Health Ontario conducted a study of health-related information collected between 2013 and 2023. The researchers focused on rates of testing and diagnoses of the following key sexually transmitted and blood-borne infections (STBBIs):

The researchers reviewed data from 269,814 positive test results; the vast majority were for conditions other than HIV. All infections were confirmed by laboratories in Ontario.

Results

Over the course of the study, rates of the four STBBIs studied increased across Ontario, particularly in the greater Toronto area, Northwestern Ontario and the region around Thunder Bay.

Some people had two simultaneous infections (co-infections), and this accounted for nearly 6% of positive test results. On average, cases of people having two simultaneous infections increased by 10% per year during the study period. Cisgender men and transgender people were more likely to have co-infections compared to cisgender females.

Co-infections were most common in Northwestern Ontario, followed closely by the greater Toronto area.

Factors increasing vulnerability to STBBIs

Males were more likely than females to have a positive test result for any of the studied infections. The researchers found that the following behaviours were linked to an increased risk for the STBBIs studied:

having anonymous sex
having sex while high
having multiple sexual partners

having condomless sex

engaging in sex work

exchanging in survival sex

injecting or inhaling drugs

It is likely that many of these factors intersected with each other. They also may have intersected with issues of unstable housing and low income.

According to the study team, people who were underhoused or experiencing homelessness were at very high risk for getting STBBIs. Additional analysis found that people who were experiencing poverty, who were otherwise marginalized and who were racialized were more likely to have STBBIs.

The researchers stated that transgender people may be more vulnerable to STBBIs because they face stigma and discrimination as well as barriers to accessing healthcare.

Possible broad-based solutions

The research team stated that “prevention programs should focus on addressing [behavioural and socio-structural] intersecting drivers [of STBBIs].” They recommended the following interventions:

expanded access to low-barrier STBBI testing
strengthened harm reduction service delivery
targeted sexual education to key populations

The researchers also stated that their study underscores the importance of “addressing structural drivers such as unstable housing and material deprivation.” They added that “strengthening Ontario’s surveillance systems to better integrate social, behavioural and structural indicators would further support the development of equitable, evidence-driven prevention strategies.”

Previous research by other teams has found that social and economic factors can negatively intersect and increase the risk for STBBIs.

Gilchrist J, Waters K, Smieja M, et al. Sexually transmitted and blood-borne infection syndemics in Ontario: A population-based retrospective study of iPHIS data (2013-2023). Canadian Journal of Public Health. 2026; in press.

From Canadian AIDS Treatment Information Exchange (CATIE).
This content was originally published by CATIE, Canada’s source for HIV and hepatitis C information.