Undetectable or Unknown? A Longitudinal Event-Level Analysis of Disclosure of HIV Serostatus and Undetectability Among Gay, Bisexual, and Other Men Who have Sex with Men (gbMSM) in Metro Vancouver

We examined temporal trends and factors associated with reporting partner's serostatus and viral load among a sample of gay, bisexual and other men who have sex with men (gbMSM) in Vancouver, Canada. Participants were recruited using respondent-driven sampling and we collected prospective cohort data from 09/2014 to 02/2017 using a computer-assisted questionnaire and nurse-administered STI/HIV testing. Our study included 481 participants reporting on 3780 sexual events. Among HIV-negative/unknown gbMSM we found a trend towards decreased proportions of sexual events reporting an unknown HIV-status partner (42-19%; p =  < 0.001) and found increased proportions among gbMSM living with HIV (11-27%; p = 0.043). More participants living with HIV reported sex with undetectable partners, compared to HIV-negative/unknown participants (14.8% versus 5%). Our multivariable model found that compared with unknown status partners, undetectable partners were older, were from longer sexual relationships and were more likely to engage in condomless anal sex. Findings indicate that HIV-negative gbMSM seem more aware of the serostatus of their partners over time, but knowledge of partners' viral load over time was not significant. Further research should assess the degree to which new campaigns such as Undetectable = Untransmittable (U = U) are associated with discussions about HIV disclosure and viral load status.