Past dynamics of HIV transmission among men who have sex with men in Montréal, Canada: a mathematical modeling study

Abstract

Background Gay, bisexual, and other men who have sex with men (gbMSM) experience disproportionate risks of HIV acquisition and transmission. In 2017, Montréal became the first Canadian Fast-Track City, setting the 2030 goal of zero new HIV infections. To inform local elimination efforts, we estimate the evolving role of prevention and sexual behaviours on HIV transmission dynamics among gbMSM in Montréal between 1975 and 2019. Methods Data from local bio-behavioural surveys were analyzed to develop, parameterize, and calibrate an agent-based model of sexual HIV transmission. Partnership dynamics, HIV’s natural history, and treatment and prevention strategies were considered. The model simulations were analyzed to estimate the fraction of HIV acquisitions and transmissions attributable to specific groups, with a focus on age, sexual partnering level, and gaps in the HIV care-continuum. Results The model-estimated HIV incidence peaked in 1985 (2.3 per 100 person years (PY); 90% CrI: 1.4–2.9 per 100 PY) and decreased to 0.1 per 100 PY (90% CrI: 0.04–0.3 per 100 PY) in 2019. Between 2000–2017, the majority of HIV acquisitions and transmissions occurred among men aged 25–44 years, and men aged 35–44 thereafter. The unmet prevention needs of men with > 10 annual anal sex partners contributed 90–93% of transmissions and 67–73% of acquisitions annually. The primary stage of HIV played an increasing role over time, contributing to 11–22% of annual transmissions over 2000–2019. In 2019, approximately 70% of transmission events occurred from men who had discontinued, or never initiated antiretroviral therapy. Conclusions The evolving HIV landscape has contributed to the declining HIV incidence among gbMSM in Montréal. The shifting dynamics identified in this study highlight the need for continued population-level surveillance to identify gaps in the HIV care continuum and core groups on which to prioritize elimination efforts.

Measuring progress towards reaching zero new HIV acquisitions among key populations in Québec (Canada) using routine surveillance data: a mathematical modelling study

“…Although we do not model the impact of ART on transmission directly, its successful scale‐up likely played a part in the incidence declines over the last decade. Moreover, pre‐exposure prophylaxis (PrEP) was introduced for MSM in 2013 and could have accelerated incidence reductions, especially amidst increased usage in recent years [42,43], where coverage (i.e. those currently on PrEP) rose from 5% to 10% between 2017 and 2018 in Montréal [43].…”

“…Moreover, pre‐exposure prophylaxis (PrEP) was introduced for MSM in 2013 and could have accelerated incidence reductions, especially amidst increased usage in recent years [42,43], where coverage (i.e. those currently on PrEP) rose from 5% to 10% between 2017 and 2018 in Montréal [43].…”

Exploring the dynamics of the 2022 mpox outbreak in Canada

“…Partnerships were classified as casual or regular (with the latter representing 40% of partnerships) 21 . As in [21], casual partnerships were assumed to start and end within the same week, and were randomly assigned 1–3 sex acts.…”

Population‐level effectiveness of pre‐exposure prophylaxis for HIV prevention among men who have sex with men in Montréal (Canada): a modelling study of surveillance and survey data

“…We used an existing calibrated agent-based model of sexual HIV transmission among Montréal MSM, described elsewhere [28]. and simulated with a 2-week time step.…”

“…suppression), HIV testing and ART (FigureS9), HIV transmission and disease progression[28]. Initialized in 1975, the model tracks a population of 10,000 MSM aged 15+ years that increases over time, reflecting Montréal's demographics.…”