January 23, 2013
Undetectable Viral Load Essentially Eliminates Transmission Risk in Straight Couples
According to a recent review of multiple studies, heterosexual serodiscordant couples have an almost non-existent risk of HIV transmission if the HIV-positive partner has an undetectable viral load as a consequence of successful antiretroviral (ARV) therapy, the National AIDS Treatment Advocacy Policy (NATAP) reports. Presenting their findings at the Third International Workshop on HIV and Women in Toronto, researchers pooled data from six different studies of serodiscordant heterosexual couples, including the famous HPTN 052, which found a 96 percent risk reduction due to ARV therapy.
Three of the studies provided data on HIV transmission rates, ARV history and viral load of the HIV-positive partner. These studies included a combined 991 couples with 2,064 person-years of follow-up. The researchers found a transmission rate of 0.0 per 100 person years.
Three additional studies, including HPTN 052, had information on just rates of transmission and treatment history, covering 5,233 couples. Factoring in these studies with the other three, the researchers found a pooled transmission risk of 0.14 per 100 person years. In other words, if 1,000 serodiscordant couples in which the HIV-positive partner is on ARV therapy with an undetectable viral load had sex for one year, about one or two of the HIV-negative partners would become infected with the virus.
All four of the transmissions in the six studies took place before six months had passed since the HIV-positive partner began ARVs and therefore may not have yet reached an undetectable viral load. Taking this into account, the researchers conducted another analysis excluding the data from these transmissions. In this case, the risk of transmission was also 0.0 per 100 person years.
Sten H. Vermund, MD, PhD, director of the Institute for Global Health at Vanderbilt University in Tennessee, cautions that even those who maintain what appears to be an undetectable viral load may still have what he describes as “viral spikes” as a consequence of a vaccine, sexually transmitted infection or other acute infection. These spikes may intermittently put a partner at risk of HIV infection.
“If you want to have your risk of transmitting to others be zero, be on antiretrovirals religiously and also use condoms,” Vermund says.
To read the conference abstract, click here.
Search: HIV, undetectable viral load, transmission, serodiscordant couples, almost non-existent risk, National AIDS Treatment Advocacy Policy, NATAP, Third International Workshop on HIV and Women in Toronto, HPTN 052, Sten H. Vermund, Institute for Global Health at Vanderbilt University.
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