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What you need to know: “Zero risk” of transmitting HIV

The World Health Organization (WHO) released a policy brief, The role of HIV viral suppression in improving individual health and reducing transmission, at IAS 2023, the 12th IAS Conference on HIV Science, in Brisbane.

What does the brief say?

According to WHO, people living with HIV who have an undetectable viral load using any WHO-approved test and continue taking medication as prescribed have “zero risk” of transmitting HIV to their sexual partner(s).

People living with HIV who have a suppressed but detectable viral load and are taking medication as prescribed have “almost zero or negligible risk” of transmitting HIV to their sexual partner(s).

An undetectable viral load is the ultimate goal of antiretroviral therapy (ART) for all people living with HIV, for their own health and to prevent transmission to their sexual partner(s) and children. As WHO explains, when a viral load is so low the test cannot measure it, we say that the person’s HIV is undetectable.

Healthcare staff providing HIV care should reinforce this message at every visit and opportunity, supporting clients to reach viral suppression – and celebrating when they do!

Why is this important?

For the first time, WHO has stated in very clear language that zero risk of transmitting HIV is attainable through adherence to appropriate HIV treatment. In addition, healthcare staff should reinforce the undetectable equals untransmittable (U=U) message.

Without doubt, this will reassure people living with HIV about treatment and adherence. It will also reduce hesitancy towards promoting U=U. Delivering clear messages about the benefits of treatment has been shown to encourage HIV testing, reduce stigma and improve HIV treatment outcomes.

WHO recommends additional options and sample types of viral load testing technologies. It emphasizes that prequalified tests and sample types, such as dried blood spot, often enable much better access to viral load testing. National programmes should consider these options to ensure that viral load testing is widely available for all people living with HIV.

This is crucial because routine viral load testing is still inaccessible for millions of people living with HIV, particularly in low- and middle-income countries. It is also important to provide CD4 cell count testing at HIV diagnosis and ART initiation for identifying advanced HIV disease.

What are the three categories of viral load levels?

  • Undetectable: No measurable virus (not detected by the test or sample type used); zero risk of transmission to sexual partner(s); minimal risk of vertical transmission

  • Suppressed (detected but ≤ 1,000 copies/mL): Almost zero or negligible risk of transmission to sexual partner(s)

  • Unsuppressed (>1,000 copies/mL): Increased vulnerability of becoming ill and transmitting HIV to sexual partner(s) and/or children

What are the takeaways from the brief?


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The IAS promotes the use of non-stigmatizing, people-first language. The translations are all automated in the interest of making our content as widely accessible as possible. Regretfully, they may not always adhere to the people-first language of the original version.