U=U is more than just a catchy slogan. In fact, what it stands for — the overwhelming evidence that a person with HIV who has a durably undetectable virus is virtually incapable of transmitting the virus to a partner — has finally been accepted and even promoted by some of the world’s top scientific bodies, including the World Health Organization, the National Institutes of Health, and the U.S. Centers for Disease Control and Prevention.

In the words of its originators and promoters, U=U (undetectable = untransmittable) represents a potential revolution not only in the world of HIV prevention, but also in the lives of people living with HIV who continue to experience stigma, discrimination and criminalization in even the most enlightened and tolerant communities, cities, states and countries.

While there continue to be quibbles about the absolutism of the assertion that U=U, such concerns are nothing new in the world of medicine and public health. Some believe in the necessity for unequivocal and simple statements to change the minds and hearts of those who need clear health messages, while others worry that words implying an absolute reality (impossible to transmit, untransmittable, etc.) can lead people to take risks they wouldn’t otherwise take. Still, the evidence is very hard to ignore.

Three major studies have documented zero HIV transmissions when the HIV-positive partner achieves and maintains a viral load under 200 copies. A large, multinational study called HPTN 052 was the first out of the gate in 2011 — and when looking only at couples where the partner living with HIV was proven to be fully suppressed (and stayed that way), there were no linked transmissions to the HIV-negative partner. Some HIV-negative partners did become infected, but genetic sequencing of the virus proved that the infection always came from a person outside of the relationship. This study was almost exclusively among cisgender female and male couples.

In 2014, another large study, PARTNER, reported similar results. Again, this study was largely among cisgender men and women, but there were substantially more same-sex cisgender male couples included than in 052. Despite thousands of episodes of condomless sex, there were no linked sex transmissions between positive and negative partners in both opposite sex and same sex couples when the partner with HIV had viral suppression. A follow-on study, called PARTNER2, is going to focus solely on same-sex male couples.

A third study, Opposites Attract, solely among same-sex cisgender male couples reported identical results in 2017, easing any remaining concern that viral suppression might be less effective at reducing transmission to an HIV-negative partner when the primary risk is through rectal exposure.

HIV, however, has never been a simple disease that lends itself easily to a perfect calculation of the odds. Like the story of the boy who cried wolf, those who raise the alarm about an imperceptible risk that never actually plays out will come to be mistrusted. Moreover, the hyper-logical wiggle room that scientists and public health officials like to leave themselves could have significant unintended consequences, including continued criminalization of people living with HIV and the perpetuation of HIV stigma. Finally, failure to embrace the U=U message is also a failure to remain consistent with a principle upon which every plan to end the epidemic has been based: that encouraging and supporting all people with HIV to have fully suppressed virus not only assures their own long-term health but is also the most effective way to rapidly quash and one day end the epidemic.

At Project Inform, we work to forward the goal of community-wide viral suppression in a number of ways, some of them obvious and others less so. Our leadership in the roll-out of the Affordable Care Act in California has led to thousands more people with HIV entering and remaining in medical care. We have also played a central role in designing and advocating for the Getting to Zero plan in San Francisco, which aims to achieve zero new HIV infections, zero HIV deaths, and zero HIV stigma by 2020. And we are now partnering with other HIV and hepatitis C agencies in California to develop a Getting to Zero plan in our home state.

Project Inform incorporates the U=U message in our health education materials for both people living with HIV and those at risk for HIV who are interested in pre-exposure prophylaxis (PrEP). The combination of U=U and PrEP has presented mixed-status couples with an unprecedented opportunity for intimacy that hasn’t existed since before epidemic flared in the early 1980s.

But U=U guides us in other less obvious ways as well. Since taking up work on viral hepatitis (particularly hepatitis C), we have long acknowledged that HIV and hepatitis are intertwined diseases that not only plague the same individuals and worsen their health outcomes, but also serve as bell-weathers of the epidemic. Addressing them as twin epidemics in need of access to adequate and culturally competent health care services allows for care engagement for both diseases, whether someone enters the system through a positive HIV test at a syringe access site or the successful completion of hepatitis C treatment and a cure.

Perhaps the least visible way that U=U is alive in our work is in the social science we conduct about HIV cure research with and for people with HIV. The consequences of having one’s virus become detectable again through participation in a clinical trial that requires stopping antiretroviral therapy carries with it more than just health concerns. Project Inform has also brought scientists and science funders to recognize that there may be significant psychological and social impacts, as well.

U=U is a transformative movement with enormous potential to increase participation in care and treatment, prevent new infections, and reduce HIV related stigma. Project Inform aims to be an active participant in that movement.

For more information on U=U, go to www.preventionaccess.org.