You've probably heard of the groundbreaking HPTN 052 study showing that a fully suppressed viral load slashed HIV transmission rates by 96 percent among heterosexual couples, but a recent French study might complicate things. It found that 13 percent of HIV-positive men who have sex with men (MSM) had intermittently detectable levels of HIV in their semen. The long-term study at the Bicetre Hospital in Paris examined MSM who were on stable antiretroviral regimens and who had an undetectable viral load for at least six months. While further research is needed to determine how this presence in the semen might affect HIV transmission rates, the researchers did find that a handful of factors were associated with a reduced risk of detectable HIV in semen, including having a CD4 cell count above 550.