High Viral Loads Linked to HIV Risk Among Black MSM
The high HIV incidence among black men who have sex with men (MSM) in the United States may be explained, at least in part, by the finding that HIV-negative black MSM, compared with white MSM, are more than twice as likely to encounter a sex partner who can transmit HIV if safer sex practices are not followed.
The incidence and prevalence of HIV among black MSM, particularly young black MSM, continue to be disproportionately high compared with those among MSM of other races or ethnicities. Yet in studies, black MSM consistently report the same or lower levels of sexual- or drug-using risk behaviors as other MSM.
The researchers created a tool—transmission potential prevalence, or TPP—to calculate how many black and white MSM participating in the study were both HIV positive and had viral loads high enough to pass it on to others.
HIV prevalence was 42 percent in the black group compared with 14 percent among the white MSM.
Incidence (new HIV cases) in the study was found to be 6.4 cases per 100 person-years among those in the black MSM group, compared with 1 case per 100 person-years in the white MSM group. “In other words, if we had 100 HIV-negative black MSM, one year later we would see six cases develop, while among 100 white [MSM] we would see one case develop over the course of a year.”
By expanding the parameters to include everyone—undiagnosed as well as diagnosed—the researchers found 25 percent of the black MSM were both HIV positive and had viral loads above 400, as compared with 8 percent among the white participants.
Translating these data into the probability of encountering a sex partner who is capable of transmitting HIV, the study found that black MSM faced a 39 percent chance that at least one partner has transmission potential, compared to 18 percent among white men at the same risk behavior level.
Rosenberg explained what this means: “To have a 50 percent chance of acquiring HIV, a black MSM needs just three partners, compared to seven for white MSM. To reach a 90 percent risk of HIV, a black man would need 10 partners, compared to 25 for white MSM.”
The researchers conclude that HIV prevention approaches that rely solely on changing risk behavior will not work to eliminate racial disparities.
They recommend that new resources aimed at preventing transmission be focused on communities with a high TPP, and that viral load measurements be incorporated into HIV surveillance measures in a manner that accounts for TPP.