Prevalence of unprotected anal intercourse (UAI) and factors associated with primary HIV infection and secondary HIV transmission among men who have sex with men (MSM) in Ontario, Canada

Published: July 21, 2010

Prevalence of unprotected anal intercourse (UAI) and factors associated with primary HIV infection and secondary HIV transmission among men who have sex with men (MSM) in Ontario, Canada

T. Myers1, S.J. Taleski1, R.S. Remis1, D. Allman1, W. Husbands2, J. Liu1, J. Maxwell2, Lamda M-Track Study Group

1University of Toronto, Dalla Lana School of Public Health, Toronto, ON, Canada, 2AIDS Committee of Toronto, Toronto, Canada

Background: To describe and compare the potential for and factors associated with HIV transmission among self-reported HIV-positive and HIV-negative MSM.

Methods: A cross-sectional, venue-based survey recruited MSM from two cities. Socio-demographic, sexual and other behavioural variables were collected using a self-administered questionnaire. Those at risk for HIV acquisition were defined as HIV-negative participants who reported UAI with HIV-positive partners or partners of unknown HIV status. HIV-positive participants who reported UAI with HIV-negative partners or partners of unknown HIV status were considered to be at risk of potentially contribute to secondary HIV transmission to their partner(s). Multivariable logistic regressions were used to identify variables associated with primary and secondary HIV transmission.

Results: Of eligible participants, 77.2% of HIV-negative (n=1,017/1,318) and 86.3% of HIV-positive (n=220/255) MSM reported anal sex in the previous six months. 14.8% (n=195/1318) HIV-negative participants reported behaviour at risk for primary acquisition while 40.0% (n=79/255) HIV-positive participants reported behaviour with potential for secondary transmission. The odds of HIV acquisition were higher among men ≥50 years compared to men < 30 years (3.3:95%CI=1.3-8.6); men with high school or less versus some post-secondary education (2.8:95%CI= 1.2-6.5); men with incomes < $20,000 versus incomes ≥$70,000 (2.7:95%CI=1.1-6.9); and with increasing numbers of casual partners, the highest being among MSM with ≥10 casual partners (OR19.3:95%CI=8.5-44.2). The odds of increased risk for secondary HIV transmission were higher among men reporting ≥10 casual partners versus those reporting no casual partners (OR 15.3:95%CI=1.9-122.7).

Conclusions: In this population of MSM, the potential for HIV transmission was high. While our analysis provides information useful for targeting prevention for HIV-negative MSM, the factors associated secondary transmission were limited and suggest risk occurs across all sub-groups of HIV-positive MSM. More in-depth research into secondary transmission and positive prevention, and the impact of sexual context, and structural factors including legislation is required.
 

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