HIV can be detected in semen of men who have an undetectable viral load in blood, according to results of a 304-man study.1 This finding underlines the importance of using condoms when having sex, even if a man is taking antiretroviral therapy and has an undetectable viral load in blood. If HIV can be detected in semen -- even at low levels -- there may be a chance that it can be transmitted to a female or male sex partner.
Several studies show that sex partners of HIV-positive people taking antiretrovirals have a lower risk of becoming infected with HIV than do partners of people not taking antiretrovirals.2-4 As a result, some HIV experts and public health officials believe everyone with HIV should start antiretroviral therapy as a way to prevent the spread of HIV. U.S. antiretroviral guidelines say everyone with HIV should start antiretroviral therapy, regardless of CD4 count.5
Some officials argue that antiretroviral-treated people with an undetectable viral load in blood and without another sexually transmitted infection can safely have sex without a condom because they are highly unlikely to pass their HIV along to a sex partner. But this proposal remains controversial, partly because studies in the past 10 years show that HIV can be detected in semen even when it is not detected in blood.
Questions about HIV transmission risk during sex are particularly important to heterosexual couples who want to have a baby although the male partner is HIVpositive. In France, where the new study was done, such couples can take advantage of "sperm washing." This technique nearly eliminates the possibility of HIV transmission from an HIV-positive man to an HIV-negative woman. But this approach requires the man to ejaculate outside the woman. Of course most couples would rather conceive a child while having sex in the usual way.
To address these issues, French researchers planned this study of blood and semen samples from HIV-positive men who wanted to have sperm washing to safely conceive a child with an HIV-negative woman.
The study focused on HIVpositive French men who requested sperm washing from 2002 through 2011. All men were heterosexual and had a stable relationship with a female partner. All men were taking combination antiretroviral therapy.
The researchers measured virus (as HIV RNA) in paired blood and semen samples from each man. The tests used to measure HIV could detect as few as 40 copies of HIV RNA per milliliter of blood and 100 copies per milliliter of semen.
In one third of the men, the researchers also used more sensitive tests to measure HIV RNA in blood and HIV DNA in blood cells. HIV DNA is the form HIV takes when resting inside cells that it infects. These sensitive tests could detect 1 copy of HIV RNA per milliliter of blood and 5 copies of HIV DNA per 150,000 blood cells.
The study involved 304 men who gave 628 paired blood and semen samples between January 2002 and June 2011. Of the 314 blood samples, 107 (34%) had detectable HIV RNA. Of the 314 semen samples, 49 (16%) had detectable HIV RNA.
Twenty of 304 men (6.6%) with an undetectable viral load in blood (HIV RNA below 40 copies per milliliter) had a detectable viral load in semen. In these 20 men, viral loads in semen ranged from a low of 115 copies per milliliter of semen to a high of 1750 copies per milliliter. All of these men were taking three or four antiretrovirals including either a protease inhibitor, a nonnucleoside reverse transcriptase inhibitor, or the integrase inhibitor Isentress (raltegravir).
Rates of detectable HIV RNA in blood and in semen did not change much over the 10-year study period (Figure 1). Even in the most recent years of the study, when men were taking the latest antiretroviral combinations, 5% to 10% of men with an undetectable viral load in blood had a detectable viral load in semen.
Figure 1. From 2002 through 2011, the percent of semen samples with detectable HIV RNA when HIV RNA was not detectable in blood did not change substantially. The overall rate was 6.6%. Numbers in parentheses are the number of men with fewer than 40 copies of HIV RNA in blood.
In a subgroup of 98 men, 55% had under 1 copy of HIV RNA per milliliter of blood and 11% had fewer than 5 copies of HIV DNA per 150,000 blood cells. Six of these 98 men (6%) had detectable HIV RNA in semen; 4 of these 6 had under 1 copy of HIV RNA per milliliter of blood, and all 6 had under 40 copies of HIV RNA per milliliter of blood.
This study clearly shows that men with an undetectable viral load in blood may have detectable HIV in semen. About 1 in 20 men who had a blood viral load below 40 copies had HIV that could be detected in semen.
Research has not determined if the low levels of HIV in these men's semen could result in HIV transmission from a man to a woman, or from a man to a man. But certainly there is some risk that a man with detectable HIV in semen can pass the virus to a sex partner.
The researchers who conducted this study believe health workers should advise couples with an HIV-positive male partner to continue using condoms during sex and to use safe techniques like sperm washing if they want to conceive a child.
Taking antiretroviral therapy lowers the risk of transmitting HIV to a sex partner. And reaching an undetectable viral load in blood greatly lower the risk of transmission. But the findings of this study suggest that the transmission risk may not be zero when viral load is undetectable in blood.
It is also important to note that the rate of detectable HIV RNA in semen with undetectable HIV RNA in blood did not change in more recent years. This finding suggests that even the newest antiretroviral combinations do not always eliminate HIV RNA in semen. Some antiretrovirals get into the male genital compartment better than others. But the researchers note two studies that found no link between antiretroviral ability to penetrate the male genital compartment and HIV levels in semen.6,7
This study included only heterosexual men. But there is no reason to assume that the main result does not apply to gay men as well: Men with an undetectable viral load in blood may have detectable HIV in semen. For now, even men who have an undetectable viral load in blood should probably use condoms when having sex.