Patients Have Low Risk of Sexually Transmitting HIV With Viral Loads Less Than 1000 Copies/mL

There is almost zero risk of sexual transmission of HIV among patients with viral loads of less than 1000 copies/mL, according to a study published in The Lancet.

At the individual level, low-level viremia, or the presence of virus in the blood, is associated with virological failure, HIV drug resistance, and worse clinical outcomes. At the public health level, low-level viremia affects disease transmission risks and therefore messaging for patients with HIV, including undetectable=untransmittable (U=U) campaigns.

The researchers noted that the public health community wanted to address how low-level viremia affects sexual transmission of HIV to ensure they provided the most accurate and ethical messaging to the public, patients with HIV, their sexual partners, and their health care providers. Consequently, this study focuses on determining the risk of sexual transmission at viral loads of less than 1000 copies/mL by summarizing relevant evidence from past studies.

To do so, the researchers conducted a systemic review, utilizing various databases to search for relevant works published between January 1, 2010, and November 17, 2022. Relevant studies included information on the public health impact of low-level viremia, the science behind U=U, and sexual transmission between serodiscordant couples, where one partner has HIV, at various levels of viremia. Excluded studies were those that did not specify viral load thresholds, did not provide quantitative viral load information for transmission outcomes, and did not define low-level viremia.

The researchers identified 244 studies that aligned with their criteria, ultimately using 8 for analysis. Across all studies, the certainty of evidence was moderate, and the risk of bias was low.

These 8 studies contained 7762 serodiscordant couples across 25 countries. Three studies showed no transmission when the partner with HIV had a viral load of less than 200 copies/mL. The remaining studies contained 323 transmission events, none of which involved patients whose disease was stably suppressed on antiretroviral therapy (ART). Among all studies, the researchers found 2 transmission cases in which the patient’s most recent viral load was less than 1000 copies/mL. However, they noted that interpreting these cases was difficult as it had been at least 50 days between the most recent viral load result and the estimated transmission date.

As a result, the researchers found no definitive evidence of HIV transmission when viral loads were less than 600 copies/mL and found possible transmissions with viral loads between 600 and 1000 copies/mL to be rare occurrences. Instead, the studies displayed that transmission occurred at viral loads much higher than 1000 copies/mL. Consequently, the risk of sexual transmission is almost zero when the partner with HIV has a viral load of less than 1000 copies/mL.

Despite their findings, the researchers identified limitations to their study, one being that the definition of low-level viremia varied across the different studies analyzed. Also, the studies contained differences in the timing and frequency of viral load testing, as well as patient follow-up, which caused imprecision within the data. The findings do not apply to transmission from mother to child or through sharing injection equipment for drug use.

Limitations aside, the authors urged providers to communicate to patients with HIV the potential health risks of low-level viremia and to reinforce that they should strive for an undetectable viral load for optimal personal health outcomes. The researchers also noted that these findings can encourage providers to promote access to viral load testing in resource-limited countries by facilitating the uptake of alternative sample types and technologies. Lastly, their findings allow health care providers to destigmatize HIV and promote ART adherence.

“The evidence showing almost zero risk of sexual transmission when HIV viral loads are less than 1000 copies per mL provides a powerful opportunity to destigmatize people who are living with HIV and promote adherence to ART through dissemination of this positive public heath message,” the authors concluded.

Reference

Broyles LN, Luo R, Boeras D, Vojnov L. The risk of sexual transmission of HIV in individuals with low-level HIV viraemia: a systematic review. Lancet. Published online July 22, 2023. doi:10.1016/S0140-6736(23)00877-2