Ask the Doc: Serodiscordant Couples and HIV Transmission

In this installation of Ask the Doc, Dr. Howard Scheiner discusses the ramifications of a new study that found that HIV-positive guys with an undetectable viral load were not giving their partners HIV, despite a variety of sexual acts used, and condoms used inconsistently.

Scheiner notes that there are still risks in this yet-completed study that you should consider when determining whether to have 'safer sex' or to use Truvada as PrEP. Among them was the fact that 16 percent of the couples in the study contracted other STIs.

And as the doc pointed out, there are times when there is more HIV in semen than in the blood. So unless you're in a monogamous relationship, 'safer sex' is still the safer choice.

Is Undetectable Uninfectable?

Q: Dear Doc, I recently heard about a study that found that HIV-positive guys with an undetectable viral load are not giving HIV to their partners. Does that mean I don't need to worry about using Truvada or even condoms anymore?

A: The answer is if you are the negative partner in a serodiscordant relationship (your partner is positive) you might not need Truvada if you are monogamous -- or think you are. In the study, 16 percent of the 282 MSM couples developed an STI, so it's your call on the condoms if you want to avoid other STIs. If this isn't your situation, read on.

The study you are referring to is the Partner Study that includes 282 MSM couples where one partner is HIV-positive and one is HIV-negative. The aim of the study is to evaluate the risk of HIV transmission (within the couple setting), where the HIV-positive partner is on suppressive antiretroviral therapy (ART) and condoms are not used consistently. Interim results were reported earlier this year at CROI in Boston. They reported a zero rate of HIV transmission through condomless sex with a plasma viral load of
However, the study is still ongoing and won't have final results until 2017. The upper limit of risk remains uncertain, particularly with receptive anal sex with ejaculation.

The study conclusions were to await more precise estimates for risk transmission and individual choice on condom use.

So, if you have having lots of sex with lots of guys, stay on your Truvada, especially if condoms are too last century for you. If you have a healthy dose of caution, keep the condoms to prevent other STIs, Hep C, HPV and just in case viral resistance pierces Truvada's force field down the line.

Is 'Safer Sex' Safe?

Q: The guys in that study reportedly engaged in 16,400 various sexual acts and didn't get HIV. I guess it doesn't matter anymore about 'safer' sex acts?

A: Safer sex has always been about reducing risk. It is clear that ART is a powerful tool for preventing transmission of HIV. That figure that you quote equates with a median of 43 sex acts/year for a couple. I'm not sure if you think this is a lot of sex (less than once/wk).

Whether that translates to virtually eliminating the risk of transmission in other non-coupled settings is the question. Two studies reported in 2012 showed that 7 percent of men had HIV detectable in their semen (up to 2365 copies/ml) at the same time that they were undetectable in blood using a lower limit of detection of 20 to 40 copies/ml.

The other study showed 25 percent of men with detectable virus in their semen when it was simultaneously undetectable in their blood. Men with STIs or urethritis were 29 times as likely to have detectable virus in their semen as men without these conditions, despite having undetectable virus in their blood. So, safer sex would still seem prudent, even with suppressed (undetectable) HIV viral load, in terms or reducing risk, or least until 2017 when the studies final results are in or some non-couple studies are reported.

Called "more than a doctor, a trusted friend" by his patients, Dr. Howard Scheiner is a true native New Yorker. He was born in the Bronx, he attended the esteemed Bronx High School of Science and City University of New York before receiving his medical education at The Mount Sinai School of Medicine. Truly a Renaissance man, in addition to his lifelong service to the medical profession, Dr. Scheiner is a published author, playwright and musical composer. Combining all his loves, he is perhaps most proud of founding "The Brent Varner Project, Inc." a charity that provides free HIV services to those in need through the Actors Fund of America.

This story is part of our special report: "Ask the Doc". Want to read more? Here's the full list.

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