Patients who take daily antiretroviral therapy have almost no risk of passing on HIV, according to a major new study published today.
The new research examines risks for patients carrying viral loads of less than 1,000 copies/mL.
The authors of a review of eight studies say their findings consolidate and reinforce previous studies that concluded there is no risk of transmitting the virus to sexual partners when people living with HIV have an undetectable viral load.
The review examined research published between January 2000 and November 2022 on sexual transmission of HIV at varying viral loads and included more than 7,700 serodiscordant (mixed status) couples in 25 countries.
The findings, published in today’s edition of The Lancet, will be presented at an official satellite session ahead of the 12th International AIDS Society Conference on HIV Science (IAS 2023) and they are published alongside a new World Health Organization (WHO) policy brief, which updates guidance for HIV treatment monitoring.
Previous research has shown people living with HIV with viral loads below 200 copies/mL have zero risk of sexually transmitting the virus, but the risk of transmission at viral loads between 200 and 1000 copies/mL was not known. The latest study says the risk is close to zero at this level of viral load.
Lead author Laura Broyles, of the Global Health Impact Group, in Atlanta, USA, said: “These findings are important as they indicate that it is extremely rare for people who maintain low levels of HIV to transmit it to their sexual partners.
“Crucially, this conclusion can promote the expansion of alternative viral load testing modalities that are more feasible in resource-limited settings. Improving access to routine viral load testing could ultimately help people with HIV live healthier lives and reduce transmission of the virus.”
Taking daily antiretroviral therapy (ART) lowers the amount of the virus in the body and reduces morbidity and mortality associated with the virus. Without it, people with HIV can have a viral load of 30,000 to more than 500,000 copies/mL, depending on the stage of infection.
Of the 323 sexual transmissions of HIV detected across all eight studies, only two involved a partner with a viral load of less than 1000 copies/mL.
In both cases, the viral load test was performed at least 50 days before transmission, which suggests the individuals’ viral load may have risen in the period following the test.
In studies that provided the full range of viral loads in partners with HIV, at least 80% of transmissions involved viral loads greater than 10,000 copies/mL.
Co-author Dr Lara Vojnov, of WHO, said: “The ultimate goal of antiretroviral therapy for people living with HIV is to maintain undetectable viral loads, which will improve their own health and prevent transmission to their sexual partners and children.
“But these new findings are also significant as they indicate that the risk of sexual transmission of HIV at low viral loads is almost zero. This provides a powerful opportunity to help destigmatise HIV, promote the benefits of adhering to antiretroviral therapy, and support people living with HIV.”
The authors acknowledge some limitations to their study, including that some of the data analysed were imprecise due to variations across the studies in the definitions of ‘low viral load’, and in the timing and frequency of viral load testing and patient follow-up.
Broyles LN, Luo R, Boeras D et al. The risk of sexual transmission of HIV in individuals with low-level HIV viraemia: a systematic review. Lancet 24 July 2023.
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