Drugs can cut HIV transmission through breastfeeding. Credit: © GettyImages

Tiny doses of anti-HIV drugs can stop babies from becoming infected with the virus in their mothers' breast milk, an African study has shown.

The finding - announced today at the International AIDS Society meeting in Paris, France - hints at a way of enabling more infants to benefit from breast milk. Babies of HIV-positive mothers stand a 15% chance of becoming infected during breast-feeding, so agencies such as the World Health Organization do not recommend it.

Milk formula isn't available to many in poorer countries. And a lack of breast milk has long-term health effects, including increased susceptibility to respiratory diseases - a major killer of infants in the developing world.

Joep Lange, chief scientific adviser of the International Antiviral Therapy Evaluation Center in Amsterdam, the Netherlands, found that a baby's chance of contracting HIV falls to less than 1% if they receive antiretroviral drugs while being nursed. He studied the offspring of HIV-positive volunteer mothers in Rwanda and Uganda.

"I'm not surprised it works, but it's very nice to know that it does," says epidemiologist Suzanne Filteau of the Institute of Child Health in London, UK.

The doses needed to protect babies are a fraction of those used to treat adults, and they are only necessary for the first 6-12 months of a child's life. So some might argue that treating infants is an affordable alternative to treating their mothers.

Not so, warns Filteau. Nursing mothers must also receive medication so that they can live to look after their children, she says: "A dead mother all too often leads to a dead baby". How to implement such a scheme without generating widespread resistance to anti-HIV drugs would also need to be addressed, she says.

"It's a compromise," admits Lange. Treating mothers - helping them and their babies to survive - is the ideal scenario, and studies suggest that it can work. But researchers estimate that only 1% of adults in sub-Saharan Africa have access to antiretroviral drugs.