A massive population-based study launched in the Western Cape and Zambia yesterday is aiming to answer the critical question whether testing large populations for HIV and immediately starting those infected on effective antiretroviral treatment programmes, could close the tap on new infections.

Heterosexual couples in long-term relationships who have sexual encounters outside their established partnership (extra-couple relationships) are one of the main drivers of the HIV epidemic in sub-Saharan Africa, according to new research published in The Lancet journal.