Last month, ahead of the International AIDS Conference in Brisbane, Australia, a landmark study published in The Lancet by Laura N Broyles and colleagues reported that people living with HIV who maintain low—but still detectable—levels of the virus (less than 1000 copies per mL) have almost zero risk of transmitting it to their sexual partners. It was a stunning result, adding compelling evidence to further bolster the undetectable equals untransmittable (U=U) HIV campaign. U=U means that individuals living with HIV who successfully sustain an undetectable viral load by consistently taking antiretroviral therapy are unable to transmit the virus through sexual activities. Establishing the link between low viral load and the absence of transmission has far-reaching implications for the prevention and control of HIV, encouraging the wider adoption of affordable viral load testing and helping to destigmatise HIV.