In a move long encouraged by advocates, the World Health Organization has reaffirmed that people with HIV who consistently take antiretroviral treatment and maintain an undetectable viral load do not transmit the virus during sex, a concept known as Undetectable Equals Untransmittable, or U=U. The WHO policy brief was released July 22 at the International AIDS Society Conference on HIV Science in Brisbane, Australia.
"The brief is a game-changer for equitable scale-up of viral load testing and clear messaging about transmission risk," Bruce Richman, executive director of the Prevention Access Campaign, told the Bay Area Reporter. "This is the first time a global health institution has recommended that health care providers use and reinforce 'zero risk' to communicate U=U. There's no room for ambiguity with 'zero!'
"When the WHO's new brief is translated from policy to implementation, millions more people living with HIV will have the assurance that their treatment is working to protect their health and their partners," he added.
The WHO brief states that people with an undetectable viral load who continue to take their medication as prescribed "have zero risk of transmitting HIV to their sexual partner(s)" and "minimal risk of transmitting HIV vertically to their children." What's more, people with a suppressed but detectable viral load "have almost zero or negligible risk" of sexual transmission. Data on the link between viral load and transmission via shared drug injection equipment are inadequate.
The WHO considers a viral load of 1,000 HIV RNA copies or less to be viral suppression, but the U.S. Centers for Disease Control and Prevention puts the threshold at 200 or less. A level below 50 is considered undetectable according to standard viral load tests, though more sensitive tests can measure lower levels.
While it has long been recognized that people with an undetectable viral load do not transmit HIV, the brief clarifies that people with suppressed but detectable virus — between 200 and 1,000 copies — also have an extremely low risk of transmission.
Advocates are urging public health officials and care providers to explicitly state that people with an undetectable or suppressed viral load have zero or near-zero risk. A group of activists took the stage at a conference session on July 24, chanting, "Sex is good, sex is fun, sex is zero risk."
The new guidance is supported by a systematic review of evidence published in The Lancet. In eight studies that included more than 7,700 mostly heterosexual couples, WHO's Lara Vojnov, Ph.D., and colleagues found no cases of sexual transmission when viral load was less than 600 copies. There were two cases of transmission when the HIV-positive partner may have had a viral load below 1,000, but these were difficult to interpret due to the timing of viral load tests.
"There is almost zero risk of sexual transmission of HIV with viral loads of less than 1,000 copies per ml," the study authors concluded. "These data provide a powerful opportunity to destigmatize HIV and promote adherence to antiretroviral therapy through dissemination of this positive public health message."
Prompt treatment and good adherence also prevent HIV disease progression and improve overall health. A recent study in The Lancet HIV showed that HIV-positive people who start treatment early and have a high CD4 T-cell count can expect to live nearly as long as their HIV-negative peers. Consistent treatment can keep CD4 cells from falling into the danger zone for opportunistic illnesses and other health problems.
According to a UNAIDS report released ahead of the conference, 29.8 million of the estimated 39 million people living with HIV worldwide are on antiretroviral treatment, up from 7.7 million in 2010. But this still leaves about 9 million people untreated and therefore at ongoing risk for disease progression and viral transmission. Children with HIV are not faring as well, with just 57% on treatment.
To increase the number of people who know their HIV status and have access to treatment, WHO calls on countries to expand the use of self-testing and to promote testing through sexual and social networks.
"For more than 20 years, countries all over the world have relied on WHO's evidence-based guidelines to prevent, test for and treat HIV infection," WHO director-general Tedros Adhanom Ghebreyesus, Ph.D., said in a statement. "The new guidelines we are publishing today will help countries to use powerful tools that have the potential to transform the lives of millions of people living with or at risk of HIV."
San Francisco AIDS Foundation CEO Tyler TerMeer, Ph.D., also weighed in.
"U=U has been an empowering message for people living with HIV, and goes a long way in helping to end stigma associated with HIV and AIDS," TerMeer, who is HIV-positive, stated. "For the WHO to now recognize that people who are undetectable present zero risk of transmission to partners is a message of hope for many."
Updated, 7/25/23: This article has been updated with comments from SFAF CEO Tyler TerMeer.
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