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August 19, 2009
New Evidence in Debate Over Treatment as Prevention
People with viral loads less than 50 copies tend to keep their virus suppressed consistently, which lends weight to the argument that such folks are unlikely to pass their infection on to their HIV-negative sex partners, according to a study published in HIV Medicine and reported by aidsmap.
A declaration by Swiss researchers sent a shockwave through the HIV community in January 2008, when they claimed that certain heterosexual people with HIV simply couldn’t pass the virus on to their HIV-negative partners, even in the absence of condom use or other barrier methods. There were some qualifiers: Both partners needed to be sexually monogamous, and neither could have a sexually transmitted infection. Also, the HIV-positive partner needed to be adherent to his or her medication and have had an undetectable viral load for at least six months before engaging in unprotected sexual activity.
A number of studies have, in fact, demonstrated that people with HIV are far less likely to transmit the virus if they have an undetectable viral load, but the Swiss declaration was the first to claim that the risk is essentially nil. One counter-argument raised by critics: People with HIV adhering to antiretroviral (ARV) therapy may experience viral blips, where their virus goes up temporarily. This could, theoretically, increase the risk of transmission if condoms are not being used.
To examine the likelihood of blips, Christophe Combescure, PhD, from the University Hospital Geneva, in Switzerland, and his colleagues from the Swiss HIV Cohort examined data on 6,168 patients who were on ARV therapy and had successive viral load tests between 2003 and 2007. Though the frequency of visits varied, most people had viral load tested once every three months.
Combescure’s team found that when people claimed to have missed no doses of their ARVs in the previous four weeks, they had an 85 percent chance of having their HIV levels remain under 50 copies consistently. Most viral load blips were transient. In people whose virus jumped to between 200 and 1,000 copies—detectable but still associated with a very low risk of HIV transmission—66 percent went back to undetectable at the next test.
This was less true for people whose virus had jumped to more than 1,000 copies—when transmission may be more likely to occur, the authors explain. Just 30 percent of them went back to undetectable. This occurred rarely however. The overall chance that a person would go from undetectable to more than 1,000 copies was just 2 percent, and if a person was on a potent three-drug regimen this dropped to 1 percent.
In the final analysis, poor adherence or an inferior regimen explained most of the viral load increases to more than 1,000 copies. The authors concede, however, that the “data leave open the possibility that unexplained rises in viral load above 1,000 copies/ml, although rare, may occur.”
These data also do not explore the possibility that viral load in the genital compartment may be much higher than in blood, and the impact that may have on infectiousness.
Search: Swiss declaration, viral load, treatment as prevention, consistent viral load
http://www.poz.com/rssredir/articles/hiv_prevention_transmission_761_17126.shtml
