Read how almost two decades of research backs the assertion that when people are on effective HIV treatment and have undetectable viral loads they can't pass the virus onto others. (Peter Nicholls)

A short history of the big discovery that redefined safe sex for HIV-positive people

Kevin Rebe
How science discovered that ARVs can bring the levels of HIV in the blood to levels so low it’s virtually undetectable – and impossible to transmit.

It's official: People on HIV treatment that have suppressed the virus to almost undetectable levels their blood, can’t transmit HIV through sex. Don't believe us? Take a look at the nearly two decades of scientific evidence that proves it and gave rise to the notion that "undetectable equals untransmittible" and a global campaign by the same name. Then read what it means for you and South Africa.

2000: Research is conducted among about 400 Ugandan sero-discordant couples (one person has HIV and the other does not). Partners living with HIV have relatively low levels of the virus in their blood and no HIV infections are recorded among their partners.

2008: The Swiss Federal Commission for HIV and Aids releases a statement saying that people on effective treatment, with undetectable levels of HIV in their blood and who do not have other STIs, cannot transmit the virus to others. The statement is not widely accepted.

2011: The HPTN 052 study finds that early ART prevents 95% of HIV transmissions among sero-discordant couples as long as the HIV-positive person has an undetectable HIV viral load. This is the first large study to find that having an undetectable viral load could make it impossible to transmit the virus.

2016: Research among more than 900 sero-discordant couples again reveals that effective ART and an undetectable viral load lead to zero new HIV infections among the couples despite 58 000 instances of sex without condoms.

Activists begin to talk about the concept of “Undetectable = Untransmittable”, or U=U, when it comes to HIV.

Listen to University College London scientist Alison Rodger present the preliminary findings of this study at the 2014 Conference on Retroviruses and Opportunistic Infections


July 2017: A three-country study with 358 gay male sero-discordant couples confirms U=U. The study is important because it proves the concept within a very high-risk group. The risk of contracting HIV from anal sex is about 18 times greater than that associated with vaginal sex, 2010 research published in the International Journal of Epidemiology shows.

October 2017: The US Centers for Disease Control issues the following statement: “When [ART] results in viral suppression … it prevents sexual HIV transmission.”

November 2017: More than 500 organisations and scientists from 67 countries, including South Africa, sign on to an international consensus statement supporting
U = U. — Compiled by Kevin Rebe

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