(P424) Population-based trends in syphilis testing from Manitoba, Canada: 2015-2022.

Background: In 2020, and at 134.3 per 100,000 population, the Canadian province of Manitoba had the highest reported rate of infectious syphilis in Canada, at over five times the national average of 24.7 per 100,000 population. In comparison, the national rate of syphilis in the United States was 40.8 per 100,000 population in 2020. The epidemic signature of syphilis in Manitoba is centred on young, marginalized heterosexual individuals in the capital city of Winnipeg, leading to a public health crisis involving congenital syphilis, prior to the COVID-19 pandemic. As screening and testing for syphilis are thought to be effective measures to reduce the incidence of syphilis, we investigated trends in syphilis testing prior to, and post the introduction of the COVID-19 pandemic in Manitoba.

Methods: We used population-based syphilis testing data from Cadham Provincial Laboratory, the sole laboratory responsible for syphilis testing in Manitoba. Testing data from calender years 2015 to 2022 were extracted. Directly age-standardized rates are reported, and Poisson regression used to model the determinants of testing rates.

Results: From 2015 to 2019, the number of individuals tested for syphilis increased annually, from 62,252 to 94,578, or an increase from 462 per 10,000 population in 2015 to 704 per 100,000 in 2019. After the introduction of the COVID-19 pandemic to Manitoba, testing rates dropped by approximately 10% in 2020. By the end of 2021, testing rates were at similar levels as 2019, at 703 per 10,000 population. In 2022, rates increased to 750 per 10,000 population, or an increase of 10% from 2019.

Conclusions: After an initial increase in testing for syphilis coinciding with a syphilis outbreak in Manitoba, testing rates decreased as a result of the COVID-19 pandemic. At the end of 2021, testing rates had mostly rebounded, and by 2022, surpassed pre-pandemic levels. Investigating heterogeneity in changes in testing rates since the start of the COVID-19 pandemic may guide targeted testing and screening strategies to control the further spread of infectious syphilis.