Despite an undetectable plasma viral load, HIV may be intermittently present in men's semen, with fluctuations occurring in the course of only an hour, aidsmap reports. However, this does not necessarily mean that the virus present is capable of transmitting to another person. Publishing their findings in PLOS ONE, French researchers studied 88 HIV-positive men who were receiving care to help with conceiving a child between 2006 and 2011.

The men were all taking antiretrovirals (ARVs) and had an undetectable viral load for at least the previous six months. The researchers analyzed 306 frozen sperm samples, which the men provided by masturbating after two to seven days of abstaining from sex. The men provided two semen samples within an hour-long period if they were able.

The researchers detected HIV in at least one sample from 17 of the men, comprising 19 percent of the study group. These men produced 23 samples with detectable HIV, or 7.5 percent of all the samples. The samples had a median viral load of 705; in 11 of them, the read was over 1,000.

There were 129 pairs of samples that were produced in under an hour. Twelve of the pairs, or 9 percent, had undetectable viral load in one and detectable virus in the other. The median viral load in these serodiscordant samples with detectable virus was 918.

It was not clear if the detectable virus in the semen posed a significant risk for transmission. Recent research would suggest that this is unlikely.

There was evidence suggesting that those taking HIV regimens based on protease inhibitors were more likely to have a detectable virus than those on cocktails based on other classes of ARVs. However, these findings were not quite statistically significant, meaning they could have happened by chance.

To read the aidsmap story, click here.

To read the study, click here.