What Does an Undetectable Viral Load REALLY Mean?

There are many well documented benefits to reducing the viral load of an HIV+ individual to an undetectable level. Unfortunately, there also remains a some haziness about the term "undetectable." In actuality, it is somewhat of a misnomer. For someone to truly have undetectable HIV would mean that the battery of sophisticated tests available could not find any virus in a person's body. Thus far there is only one case of an HIV+ individual, an American living at the time in Germany who received a bone marrow transplant from a donor who had a genetic resistance to the virus, who seems to have cleared HIV entirely from one's system. An undetectable viral load means that the HIV virus in one's blood has been suppressed to the point where either the HIV RNA is not present in your blood at the time of testing or that the level of HIV RNA is below the threshold needed for detection. Another factor is the sensitivity of the specific test that is utilized.

Viral suppression, as its called, may allow for the partial rejuvenation of one's immune system, thereby making one less vulnerable to certain opportunistic diseases. Perhaps one of the most intriguing recent findings (HPTN 052) is that viral suppression may help to reduce HIV transmission in sero-discordant heterosexual couples (where only one of the two is HIV+) by as much as 96%. An earlier study with MSM found an approximately 60% reduction. However, 60 or even 96 percent is not 100%.

The 2010 International AIDS Conference highlighted the following:

  • With heterosexuals with one or both using antiretroviral treatment the risk of HIV transmission is low, but not zero.
  • In male same-sex partnerships, HIV transmission risk gets higher with repeated exposure.
  • In presence of other sexually transmitted infections (STIs), HIV transmission is increased. STI seem to have a synergy with HIV and can increase the genital viral load in a HIV+ person. Moreover, a person who is HIV- but already has other STIs is actually more susceptible to HIV infection.

Now, a recent study of HIV+ MSM by Boston University School of Medicine found the presence of detectable HIV in the semen of approximately one-quarter of the men studied people with supposedly undetectable (through blood tests)viral loads. The researchers added that a major factor in the results of this study had to do with the high level of STIs in the study participants. While the study did not specifically look at whether these men were more likely to transmit HIV, it should serve to remind us that aggressive HIV treatment alone will not stop HIV transmission and that the importance of knowing one's status, treatment for STIs and condom use all remain as very important tools.