A new anti-HIV drug is to be tested on infected women in Malawi, to see if it reduces the chance of the virus been passed on to babies through breastfeeding.

Trials have shown that navaripine, a drug developed in the United States, reduces the risk of a mother with HIV infecting her child at birth.

The decision to look at its possible wider effectiveness was reached after a two-year study of babies in Malawi.

The study appears to confirm a long-held theory that breastfeeding mothers are more likely to pass on the HIV virus in the first six months of a child's life, although the risk remains until the child is weaned.

The drug is to be tested on women throughout sub-Saharan Africa.