Infection rates among mothers ranged from 15.6% in the sparsely populated Northern Cape to 43.9% in KwaZulu-Natal, which is the hardest hit region in the country.

Babies aged between four and eight weeks between June and December last year were tested at 580 sites across South Africa. The study will be repeated this year and in 2012 to evaluate transmission rates over three years and the babies will be tracked until they are 18 months old.

Last year, South Africa introduced new anti-AIDS drugs guidelines that include treatment for mothers at an earlier stage of illness.