A Canadian survey of men who have sex with men (MSM) found that among HIV-negative men, pre-exposure prophylaxis (PrEP) use was associated with a higher likelihood of having HIV-positive male sex partners and a lower likelihood of having HIV-negative partners not taking PrEP, aidsmap reports.

This finding signals what may be the beginning of an enduring shift in sexual behavior patterns in areas where PrEP has gained a major foothold. Over the decades, MSM have engaged in what’s known as serosorting—that is, engaging in sex with men of the same HIV status. With the advent of PrEP as well as the scientific awareness that fully suppressing the virus with antiretroviral (ARV) treatment blocks transmission, serosorting appears to be on the decline.

On the rise is PrEPsorting, or pharmasorting, in which MSM favor sexual partners based on whether they are on ARVs. Men on PrEP may favor other men on PrEP or HIV-positive men who are on ARVs.

Linwei Wang, PhD, of St. Michael’s Hospital in Toronto, and her colleagues conducted a survey of 1,179 MSM in Montreal called Engagement Montreal in 2017 and 2018. They published their findings in the American Journal of Epidemiology.

The study asked about the number of all sexual partners during the previous six months who had HIV, were of an unknown HIV status or were HIV negative, regardless of whether they had oral or anal sex. It also asked about the men’s past five partners, including the type of sex and whether they had known the men’s HIV status prior to having sex with them.

The HIV-negative men were asked about whether during their most recent sexual encounter either they or their partners were using PrEP.

The men had an average age of 34 years old, and 38% were non-French or non-English Canadian. Eighteen percent said they were living with HIV, 9% did not know their HIV status and the remainder did not have the virus.

A total of 14% of the HIV-negative men had used PrEP during the previous six months. Ninety-six percent of the HIV-positive men were on ARVs, of whom 92% had a fully suppressed viral load.

The men did not know the HIV status of 44% of their partners. Based on the men’s age and the demographics of MSM in Montreal, if the men’s sexual pairings had occurred by chance, 76% of their partners would have been HIV negative and 24% would have been HIV positive.

Sixty-six percent of the HIV-positive men’s partners whose HIV status they knew were also living with the virus. Eighty-eight percent of the HIV-negative men’s partners whose HIV status they knew did not have the virus.

Chance would have dictated that 29% of the HIV-negative men’s partners were on PrEP. In fact, among those who were on PrEP, 51% of their partners were also taking PrEP.

To read the aidsmap article, click here.

To read the study abstract, click here.