Is safe-sex necessary in an age of undetectable HIV viral loads? Yes.

I’ve heard people with HIV, who have undetectable viral loads, ask whether they still have to practice safer sex.

At first glance, the logical answer would seem to be “No.” No virus present, so no chance of infecting someone else, right? So why wear a condom?

But let’s think about that a little.

In 2008, the Swiss Federal Commission for HIV/AIDS stated that “after review of the medical literature and extensive discussion, [we] resolve that an HIV-infected person on antiretroviral therapy with completely suppressed viremia (“effective ART”) is not sexually infectious, i.e., cannot transmit HIV through sexual contact.”

Their conclusion was based on just a few research studies in heterosexual couples. Each study following about 400 couples for about two years. These studies were conducted in Europe and Africa. In most circumstances, the male partner was HIV positive and the female was HIV negative. The studies mention that the couples engaged in vaginal intercourse. No mention was made of whether the couples had anal intercourse. These couples did not practice safer sex. The HIV positive partner was on antiretroviral medications and had reached an undetectable viral load level. In these studies, the HIV negative partner remained HIV negative.

Note that these are relatively small studies in which the couples were followed for a short time. The Swiss physicians generalized from these results that safer-sex doesn’t seem to be necessary in adequately-treated HIV positive patients.

A few points to consider about that conclusion. We don’t know how sexually-active the couples were. A couple having sex three times per month would have a lower risk of transmitting HIV than a couple having sex twice a day. We also don’t know if there were any instances of anal intercourse. There may be a different degree of risk if anal intercourse occurred vs. vaginal intercourse. The couples were monogamous. If they had not been, there would be a risk of developing another STI, which could increase the viral load and increase the risk of infecting the uninfected partner (more on that below).

Let’s also take a look at a few other factors.

Does “undetectable” viral load equal “no virus”? Not really. It just means that the virus, if present, was there in numbers too small to be found by current methods of testing. So there may be a few particles or none in the tiny volume of blood tested. Both would give a result of “undetectable.” But, let’s say that, indeed, there is no virus present when the test is done. In that case, is it safe to go condom-free? Well, think about that. The test measures HIV at one point in time. Someone who has an undetectable viral load on Wednesday at 2 PM (when the specimen was drawn) may have a viral load of 600 three weeks later. Viral load measurements can vary in a patient on antiretrovirals from test to test. A concomitant infection with some other organism, might cause a temporary spike in HIV particle numbers.

Also, the test is searching for HIV particles in blood. It’s not telling us if virus is present in seminal fluid, and, if present, how much is there.

HIV/AIDS ribbon via Shutterstock

HIV/AIDS ribbon via Shutterstock

Additionally, the World Health Organization and the Centers for Disease Control, after looking at the same data and the statement by the Swiss Federal Commission for HIV/AIDS, both reiterated that safer sex techniques should be continued by persons who are HIV positive, regardless of level of viral load. And, of course, condoms can also help prevent the transmission of other STIs like gonorrhea and syphilis.

One more thing to consider: Even if the risk is extremely low, HIV is still not curable, and still significantly decreases the lifespans of most of the people affected.

So, based on the data, the statement from the Swiss might be correct for certain scenarios. But I think that there are several unanswered questions that need to be investigated before making a blanket statement supporting unprotected sex in HIV positive patients with undetectable viral loads.


Mark Thoma, MD, is a physician who did his residency in internal medicine. Mark has a long history of social activism, and was an early technogeek, and science junkie, after evolving through his nerd phase. Favorite quote: “The most exciting phrase to hear in science... is not 'Eureka!' (I found it!) but 'That's funny.'” - Isaac Asimov

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