By Lisa Rapaport

(Reuters Health) – Most men with HIV know whether they have enough of the virus in their blood to make them contagious, but a new study suggests one in five may mistakenly think they can’t spread the virus even when they can.

For the study, researchers examined survey data from 314 HIV-positive men who have sex with men and were in relationships with HIV-negative partners. Participants got blood tests to see if they had undetectable viral levels: so little virus in their blood that it can’t be found in lab tests or transmitted to partners.

When asked, 72.5% of men accurately reported whether they were virally suppressed, with HIV at undetectable levels, or not. Most men who knew their status, 62.5% of the participants, said they were virally suppressed and this was confirmed by blood tests done as part of the study. Another 10% of men had lab work confirming their self-report that they were not virally suppressed, and were therefore contagious.

But one in five men said they were virally suppressed and had blood tests showing this wasn’t true. Another 7.5% of men said they were contagious, but based on lab tests done during the study, they were not.

These results suggest some HIV-positive men may not fully understand the public health message that “undetectable equals untransmittable,” or U=U, said lead study author Rob Stephenson of the Center for Sexuality and Health Disparities at the University of Michigan in Ann Arbor.

“U=U is a major advance in prevention science,” Stephenson said by email. “We know it works – virally suppressed men will not transmit HIV – but for U=U to work requires men to (know) whether they are virally suppressed.”

Men in the study who mistakenly said they were virally suppressed might not be intentionally lying, Stephenson added. Instead, they might not understand that viral levels change over time or that previous test results may not reflect their current status.

“A doctor may have told you six months ago that you were virally suppressed and you hold this as a static truth,” Stephenson said.

Although there’s no cure for HIV, the virus can become undetectable when there are too few copies of it in the blood to show up on standard blood tests. But copies can multiply if people stop taking antiviral medications.

Nearly every man in the study said he was taking antiviral drugs that can help prevent full-blown AIDS and also help lower viral levels to the point where the virus is not transmissable.

Most of the men had also seen an HIV provider in the past year, the study found. But almost half of them didn’t take their medicines consistently.

“There may be a lack of education as to how viral load can change, particularly if antiretrovirals are missed,” Stephenson said.

Beyond its small size, limitations of the study include a lack of blood tests over time to help measure how consistently men took antivirals, the study team notes.

Still, the results suggest that better education may help prevent the spread of HIV among men who have sex with men, said Julia Marcusa, a researcher at Harvard Medical School and Harvard Pilgrim Health Care Institute in Boston, who wasn’t involved in the study.

“For U=U to work as an HIV prevention strategy, people living with HIV need to have an up-to-date understanding of their viral suppression status,” Marcus said by email.

To get this, patients need regular checkups with HIV specialists, and providers need to make sure men understand that U=U is 100% effective at preventing transmission to partners, regardless of condom use, as long as men really do have viral loads too low to find with blood tests, Marcus said.

“Regular medical visits with viral load testing are critical but not enough on their own,” Marcus added.

SOURCE: Journal of Acquired Immune Deficiency Syndrome, online January 7, 2020.