Elise Gork, University of Manitoba

Elise Gork (Department of Medical Microbiology & Infectious Diseases, University of Manitoba), Mikayla Hunter (Department of Medical Microbiology & Infectious Diseases, University of Manitoba), Neve Battle (Department of Medical Microbiology & Immunology, University of Alberta), Nicole Wilson (Department of Immunology, University of Manitoba), Andrea Visnjevac (Department of Medical Microbiology & Immunology, University of Alberta), Hannah Wallace (Department of Medical Microbiology & Infectious Diseases, University of Manitoba), Lynora Saxinger (Department of Medicine, University of Alberta; Department of Medical Microbiology & Immunology, University of Alberta), Jared Bullard (Cadham Provincial Laboratory, Winnipeg), Megan Halbrook (Department of Epidemiology, University of California, Los Angeles), Nicole A. Hoff (Department of Epidemiology, University of California, Los Angeles), Ryan Noyce (Department of Medical Microbiology & Immunology, University of Alberta; Li Ka Shing Institute of Virology, University of Alberta), Don Vinh (Division of Infectious Diseases, Department of Medicine, McGill University Health Center), Rusty Souleymanov (Faculty of Social Work, University of Manitoba), Placide Mbala-Kingebeni (Institut National de Recherche Biomedicale (INRB), Kinshasa Democratic Republic of the Congo), Anne W. Rimoin (Department of Epidemiology, University of California, Los Angeles), Vanessa Meier-Stephenson (Department of Medical Microbiology & Immunology, University of Alberta; Department of Medicine, University of Alberta; Li Ka Shing Institute of Virology, University of Alberta), Jason Kindrachuk (Department of Medical Microbiology & Infectious Diseases, University of Manitoba)

Discovering & Evolving

Introduction: The 2022 and 2024 mpox public health emergencies of international concern (PHEIC) highlighted that many populations are at risk for mpox. In addition, the cessation of the global vaccination program following smallpox eradication in 1980 has resulted in an increasingly immune naïve population. During the 2022 PHEIC, infections were highly concentrated among gay, bisexual, and other men who have sex with men (gbMSM), a priority population for vaccination in Canada. While vaccination resulted in rapid reductions in reported cases, concerns have been raised regarding undocumented virus circulation. Investigation of mpox seroprevalence among at-risk populations will further knowledge of ongoing virus transmission and circulation. Methods: Dried blood spots (n=267) were collected between June 2024 and December 2025 via community-based organizations and sexual health clinics in Manitoba and Alberta. Eligibility was based on provincial mpox vaccine eligibility including gbMSM, gender diverse individuals, and sex workers. Samples were analyzed using the Meso Scale Discovery V-PLEX Orthopoxvirus assay and stratified by birth year to account for potential historical smallpox vaccination. Results: After excluding those who were vaccinated, seroprevalence was 6.58% (11/167) among individuals born post-1980. Seropositive individuals included those identifying as 2SLGTBQIA and heterosexual individuals, and both men and women. Of the total samples, 14% reported mpox vaccination (Median age=36). Most individuals identified as gay (53%), cisgender (41%), or as male (72%). Among 45 sex workers, only two individuals reported vaccination. Conclusions: These results highlight undocumented orthopoxvirus exposures in the Canadian Prairies and misalignment between mpox vaccine eligibility and those with orthopoxvirus exposures.