7th International AIDS Society Conference, Kuala Lumpur, June 2013:
Reflecting the results reported from a few other studies, the French ANRS EP49 study showed that despite having well controlled blood viral load, nearly 1 in 10 HIV-positive men who have sex with men had a low but detectable HIV level in semen at some point.
Researchers took two sets of samples of blood and semen spaced four weeks apart from 157 men who have sex with men. All were on stable HIV regimens and had blood viral load <50 copies for at least 6 months before starting the study. Average CD4 count was 637, and all men were sexually active.
After testing, HIV was detected in 23 samples of semen, at a rate of 7.6%. (From other studies, the average HIV “shedding” rate is about half this in heterosexual men.) Average viral load in semen was 145 copies, within a range of 50–1,475 copies. Although 32 men had at least one asymptomatic STI such as syphilis or gonorrhea, this did not independently predict the viral load found in semen. No one had herpes simplex 2.
The first of two factors that predicted detectable viral load in semen was a current CD4 count below 554 (increased risk 70%). The second was a higher level of HIV DNA (>318 copies/million immune cells) in blood (tripled the risk).
Although a few large studies have shown a greatly lower risk of transmission when the HIV-positive partner is on stable HIV treatment, the virus can still “shed” in other body fluids such as semen. Whether these low quantities of HIV are infectious are still unknown at this time.