By: Dr. Geoffrey Modest
One issue that comes up a lot is the transmissability of HIV in serodiscordant couples when the HIV-positive person has a suppressed viral load. A letter-to-the-editor was just published, reviewing 6 relevant studies (see doi.org/10.1097/QAI.0000000000000471). Lacking the best data, the researchers assumed that a surrogate for suppressed viral load was if the HIV-positive partner had been on combined antiretroviral treatment (cART) for >6 months (since usually the viral load is suppressed by then). They found:
–At most one transmission in 113,480 sex acts, of which 17% were not condom-protected.
–For that one transmission, data were not adequate to see if it happened before or after than 6-month mark
–So, their estimation varies as follows:
–Case 1: no transmission after 6 months — upper bound of risk-per-sex act was 8.7 per 100,000
–Case 2: 1 transmission after 6 months — upper bound of risk-per-sex act was 13 per 100,000
Then, they added the results of the PARTNER study presented at the CROI (conference on retroviruses and opportunistic infections) meeting in Boston in 2014 (see here), which looked at 767 HIV-discordant couples (40% gay) where there was condom-less sex and the HIV-infected partner had a viral load –NO transmissions so far!!! (the study will go on to 2017 — this is only an abstract of an interim report from the meeting)
–So, by adding this data to the above 6 studies, the estimates for case 1 above decreased to 5.2/100,000 sex acts and from case 2 to 7.9/100,000 sex acts
So, this is helpful. However, there needs to be more data on gay couples, since most of the above is on heterosexual couples. I do have some concern about reported discordance between suppressed viral load in blood and in semen. The studies I’ve seen are mostly in MSM (men who have sex with men), so I do have concern about the relative lack of data in the above studies about MSM. One recent article from Boston found that of 83 men with undetectable HIV in blood, 25% had HIV in their semen with HIV levels of 80 to 2560 copies/mL, with multivariate analysis showing sexually-transmitted infections/urethritis and unprotected insertive anal sex with an HIV-infected partner to be independent predictors of seminal fluid HIV detection (see AIDS 2012, 26:1535–1543). Other studies have found detectable semen HIV levels in MSM with non-detectable plasma HIV levels in those with herpesvirus infections (eg CMV or EBV). But the study above is pretty reassuring, suggesting that transmission is still pretty rare (though likely non-zero). So, I think patients should still be warned that there is still a possibility of getting HIV infection if they don’t use condoms, as well as the variety of other potential sexually-transmitted infections.