World Health Organization (WHO) Reaffirms Zero Risk of HIV Transmission for Those with Undetectable or Suppressed Viral Load
In a policy brief released this week, the World Health Organization (WHO) once again emphasized that individuals living with HIV who have an undetectable viral load cannot transmit the virus to their sexual partners. This statement, known as “undetectable equals untransmittable” (U=U), has been supported by numerous health organizations.
However, the WHO’s policy brief goes further by stating that even individuals with a suppressed but detectable viral load have an “almost zero or negligible risk” of transmitting HIV. The brief defines three categories for HIV viral load measurements: unsuppressed (more than 1,000 copies/mL), suppressed (detected but less than 1,000 copies/mL), and undetectable (viral load not detected by the test used).
Recent studies have focused on the risk of transmission in individuals with low-level viral loads, defined as under 1,000 copies per milliliter. A systematic review published in The Lancet analyzed data from 7,762 serodiscordant couples across 25 countries. The review identified two cases of HIV transmission when the HIV-positive partner had a viral load between 200-1,000. The majority of transmissions occurred when the viral load was above 10,000.
However, it is important to note that in the two cases of transmission identified, there was a significant time gap between the viral load test and the transmission event. This indicates that the viral load may have been different at the time of transmission.
The authors of the review concluded that there is “almost zero risk” of sexual transmission with viral loads under 1,000 copies per mL. These findings have the potential to destigmatize HIV and encourage adherence to antiretroviral therapy (ART).
“The brief is a gamechanger for equitable scale-up of viral load testing and clear messaging about transmission risk,” said Bruce Richman, executive director of the Prevention Access Campaign. He also highlighted that this is the first time a global health institution has recommended using “zero risk” to communicate U=U, leaving no room for ambiguity.
The importance of HIV treatment in reducing transmission rates is widely recognized. UNAIDS is urging all countries to aim for a 90% reduction in HIV transmission by 2030, compared to 2010 figures. Western European countries, including the UK, are on track to achieve this target. However, the United States continues to lag behind.
In a separate development, the district of Inner Sydney in Australia reported a remarkable 88% reduction in HIV infections since 2010. This area, known as a gay hotspot, used to have the highest rate of HIV transmission in the country. The success can be attributed to high rates of HIV testing, early initiation of treatment to reduce viral loads, and the use of pre-exposure prophylaxis (PrEP). While this achievement is commendable, it is important to continue efforts in other areas of Sydney to replicate these results.
The reassurance provided by the WHO’s policy brief will undoubtedly benefit serodiscordant couples who have concerns about small rises in viral load. Even for individuals with suppressed but detectable viral load, the risk of transmission is deemed “zero or negligible”. This promotes a clearer understanding of HIV transmission risks and fosters a more inclusive and stigma-free environment for individuals living with HIV.