An international study has demonstrated that antiretroviral therapy blocks the spread of HIV from an infected person to their uninfected partner, according to New Scientist.

The study involved 13 countries and 1763 couples, in which one partner carried the infection at the outset.

In 886 of the couples, the infected partner received antiretroviral drug therapy (ART) from the outset, while treatment was delayed in the other 877 couples until the infected partner showed pre-defined signs of sickness.

Preliminary results showed that only one of the 886 individuals who received immediate treatment passed the virus to their partner. Twenty seven cases of cross-infection occurred in the 877 couples with delayed treatment.

The study was stopped about three to four years early so all of the couples could be treated.