Undetectable Viral Load — Not a Guarantee Against Transmitting HIV

Summary and Comment |
April 23, 2012

Undetectable Viral Load — Not a Guarantee Against Transmitting HIV

  1. Charles B. Hicks, MD

Detectable HIV RNA in semen concurrent with undetectable plasma HIV RNA is not an uncommon event, a finding which may have implications for HIV transmission.

  1. Charles B. Hicks, MD

Results from the HPTN 052 trial demonstrated antiretroviral therapy (ART) to be a powerful tool for both treatment and prevention, reducing the likelihood of HIV transmission by 96%. Some experts have suggested that suppression of HIV to undetectable levels in plasma virtually eliminates the risk for transmission, and in 2008, the Swiss Federal AIDS Commission declared that HIV-infected individuals on “effective ART” were “sexually noninfectious” if they did not have any other sexually transmitted infections (STIs). However, data from two recent studies suggest the need for caution.

Lambert-Niclot and colleagues evaluated 628 paired blood and semen samples collected from 304 HIV-infected men seeking assisted reproductive technology support between 2002 and 2011. Twenty men (6.6%) were found to have detectable HIV RNA in semen at the same time that they had undetectable HIV RNA in plasma, using an assay with a lower limit of detection of 20 to 40 copies RNA/mL. Seminal HIV RNA levels ranged from 135 to 2365 copies/mL. All 20 men had been on continuous suppressive ART for >6 months, and none had a concomitant STI. Sixteen had at least one subsequent concordant result (both samples with undetectable HIV RNA), most while on the same ART regimen as when the discordant result was noted. The prevalence of discordant blood/semen results did not change over time nor did it seem to be related to the specific antiretrovirals being used.

In a separate study, Politch and colleagues evaluated paired blood and semen samples from 101 HIV-infected men on stable ART, nearly all of whom reported sex with men. Overall, 21 (25%) of the 83 men with undetectable HIV in blood simultaneously had detectable virus in semen — a surprisingly high proportion attributed in part to the presence of STIs or urethritis in 10% of the men and genital inflammation in 24%. Men with STIs or urethritis were 29 times as likely as men without these conditions to have detectable HIV in semen despite undetectable virus in blood. Unprotected insertive anal intercourse and the presence of genital inflammation were also significantly associated with increased likelihood of a discordant blood/semen result.


Although there is no doubt that ART significantly decreases the likelihood of HIV transmission, these data indicate that the risk for HIV transmission is not eliminated by suppressive ART. Shedding of virus in the male genital tract is not uncommon, even in men with consistently undetectable plasma HIV RNA. Among such men, STIs, urethritis, and genital inflammation significantly increase the likelihood of HIV shedding in semen, and the timing and frequency of this shedding appear to be unpredictable. Furthermore, previous studies have shown no clear association between the presumed penetration of specific antiretrovirals into the genital tract and the likelihood of detectable virus in semen. Thus, despite the fact that the threshold level of genital-tract HIV necessary for transmission is not known, caution is warranted. Recommending safer sex (and procreation) practices for all HIV-infected patients, even those with suppressed plasma HIV RNA, seems prudent.


Reader Comments (1)

Bernard Hirschel

I'd like to point out an additional reason why, in Doctor Hicks' words "Recommending safer sex (and procreation) practices for all HIV- infected patients, even those with suppressed plasma HIV RNA" is indeed advisable. Imagine, as is likely, these recommendations are not followed. Then, if something bad happens, the onus is on the patient. As physicians, we should always try to shift responsibility for mishaps to our patients, and one of the means of doing so is issuing maximalist precautions. It makes our practice so much easier.

Competing interests: None declared

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