The AIDS virus can be passed from an infected mother to her baby if she pre-chews the child's food, scientists have discovered.

The US Centers for Disease Control and Prevention said it had identified three cases in which a child was infected in this way between 1993 and 2004.

The mother was involved in two of the cases and a relative who acted as a caregiver was involved in the third.

It was already known that HIV can be found in the saliva, tears and urine of infected individuals, but there were no recorded cases of infection by these secretions to date.

The three main transmission routes of HIV are sexual contact, exposure to infected body fluids or tissues and from mother to fetus or child during prenatal period.

MHE/DT