New York—One of the issues in HIV prevention is determining when viral load becomes low enough from use of antiretroviral therapy that the infection is no longer transmittable.

Public health officials are now promoting the concept that "Undetectable Equals Untransmittable,” abbreviated as “U=U.” The CDC estimates that the strategy is completely effective against the sexual transmission of HIV.

Now, a new study of nearly 112,000 men who have sex with men in the U.S. suggests that the U=U message is gaining widespread acceptance.

The study in the Journal of Acquired Immune Deficiency Syndromes notes that past research has identified no linked HIV transmissions in serodifferent sexual encounters where the partner with HIV has an undetectable viral load (VL). “As a result, awareness and dissemination of treatment as prevention (TasP), and movements like “Undetectable = Untransmittable” (U=U), have grown,” write the authors from Hunter College of the City University of New York.

An online cross-sectional survey from November 2017 through September 2018 gathered data from 111,747 sexual minority men (SMM) in the United States. Participants provided sociodemographic data and answered questions regarding biomedical status, HIV and STI prevention behaviors, drug use, condomless anal sex, and perceived accuracy of the U=U message. Researches then analyzed the information to better understand factors associated with perceived accuracy of U=U stratified by HIV status.

Results indicate that, overall, 53.2%% of the sample perceived U=U as accurate, with the highest rates among HIV-positive SMM (83.9%), followed by HIV-negative (53.8%) and status-unknown (39.0%) SMM. In fact, models showed a 2% to 3% increase per month in accuracy beliefs among SMM.

“Consistent with prior work, there was greater heterogeneity among HIV-negative and unknown men, with several factors differentiating perceived accuracy, compared to SMM with HIV,” according to the researchers. “Perceived transmission risk levels with undetectable partners were skewed well above accurate levels, and perceptions of transmission risk was associated with lower perceived accuracy of U=U.”

The authors assert, “Public confidence in [treatment as prevention] and U=U are growing, but clear, unequivocal messaging about the effectiveness of U=U is critical. Due to misunderstandings of risk, language that focuses on protective benefits rather than transmission risks may reach more people and allow better comparisons with PrEP and condoms.”

“A growing number of sexual minority men believe that U=U is accurate, but our data suggest that most still overestimate the risk of HIV transmission from an undetectable partner, which may be because people have trouble understanding the concept of risk,” explained lead author Jonathon Rendina, PhD. “All published studies point to undetectable viral load as being the most effective method to date of preventing sexual HIV transmission, but most of our messaging has focused on the level of risk being zero rather than describing it in terms of effectiveness, which is the way we usually talk about condoms and PrEP.”

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