ONE new meta-analysis eight published studies found that the risk of sexually transmitting HIV is almost zero in people with a low viral load. This study confirms and extends the message that “Undetectable=Untransmittable” or “U=U,” which encourages people living with HIV to stay on drug treatments both for their own health and to prevent transmission of the virus to partners. Until now public health has focused on undetectable viral loads (less than 200 copies of the virus per mL of blood), but this study shows that low viral loads (less than 1,000 copies/mL) may offer the same benefits in terms of sexual intercourse transmission.
Viral load refers to the amount of virus in the blood of someone living with HIV. The goal of antiretroviral therapy (ART) is to suppress the viral load so that the immune system can continue to function and a person can stay healthy and live longer. Without ART, people living with HIV can have viral loads between 30,000 and 500,000 copies/mL depending on the stage of infection. A viral load of less than 1,000 copies/mL is considered suppressed and anything below 200 copies/mL is considered undetectable.
The analysis, which was presented at the International AIDS Society on HIV Science meeting and published in the Lancet, included 7,762 HIV-discordant couples (couples in which one partner has HIV and the other does not) in 25 countries. Between them, it was total 323 sexual transmissions of HIV were identified, and only two involved a partner with a viral load of less than 1,000 copies/mL. The authors note that in these two cases there was a long time gap (more than 50 days) between viral load testing and transmission to a partner, which could mean that the person’s viral load had increased without their knowledge.
Lara Vojnov, consultant diagnostics in the HIV and hepatitis division at the World Health Organization (WHO), was a co-author of the study. She explained its meaning as follows:
“The ultimate goal of antiretroviral therapy for people living with HIV is to maintain undetectable viral loads, which will improve their health and prevent transmission to their sexual partners and children. But these new findings are also important because they indicate that the risk of sexually transmitting HIV at low viral loads is almost nil. This provides a powerful opportunity to help destigmatize HIV, promote the benefits of antiretroviral treatment adherence and support people living with HIV.”
The study was released alongside a new policy summary by the WHO which focuses on the importance of suppressing the virus. The summary suggests that providers should emphasize the goal of suppression to all people living with HIV, particularly those new to treatment, and that viral load testing can serve as a motivator for treatment adherence. He also explains that there are many approved types of viral load tests. The summary suggests that point-of-care testing and alternative sample types (such as dried blood spot) could greatly expand the availability of testing in low-resource and remote areas of the world.
Bruce Richman, found in the Prevention Access campaign, he said: “WHO’s clarification that an undetectable viral load can be confirmed by any WHO-approved test is a game-changer for health equity, particularly in lower-income countries where plasma-based testing is not cost-effective and expandable. When the new WHO update is translated from policy into practice, millions more people living with HIV will be reassured that they remain healthy and cannot transmit HIV.”
Both the article and the policy brief also stress that the findings about low viral loads apply only to sexual transmission of HIV. The impact of viral load on HIV transmission through needle sharing for injecting drug use has not been studied. In terms of mother-to-child transmission, the risks are different because transmission can occur during pregnancy, childbirth or breastfeeding which means exposure to the virus is higher (both in duration and intensity) . However, the policy paper notes that, “Available evidence suggests that if a mother living with HIV receives antiretroviral therapy and maintains a suppressed viral load during pregnancy, delivery, and breastfeeding, the risk of vertical transmission of HIV may be as low as <1%.
Read the full WHO policy brief, The role of HIV suppression in improving individual health and reducing transmission policy, here.
