'It's Primarily Around Their Viral Load': Public Health Decision-Making and HIV Risk Assemblages in Ontario, Canada.

In Ontario, Canada, public health authorities can issue and enforce orders to people living with HIV (PLWH). However, how public health practitioners determine when someone's behaviours constitute 'significant' risk remains underexplored. We drew on assemblage theory to examine how HIV risk is co-constituted through the interplay among biomedical technologies, institutional practices, legal frameworks and social discourses. We conducted 18 semi-structured interviews with public health personnel and used reflexive thematic analysis. Five interrelated themes emerged. First, high viral load was considered a potential risk indicator when associated with high-risk activities. Second, discontinuity in HIV care may flag individuals for intervention. Third, co-infection with sexually transmissible and blood-borne infections (STBBI) triggered a viral load review to assess HIV exposure potential. Fourth, noncompliance with public health directives positioned PLWH as needing management. Fifth, Undetectable = Untransmittable (U = U) discourses have reconfigured and neutralised risk, functioning as a technology of reflexive governance. However, uptake of U = U was described as uneven across Ontario's public health units, leading to variable, and sometimes coercive, approaches. By conceptualising HIV risk as emergent, this study challenges individualised notions of responsibility and highlights the relational production of risk. Adoption of U = U and equity-based public health practices is needed to ensure nonpunitive HIV responses.