U.S. researchers said they have “compelling evidence” that three infants have contracted HIV by eating food pre-chewed by their positive caregivers, a transmission route that has been not previously reported and has important global implications, Reuters reports. Their study is published in the latest issue of Pediatrics.

According to the article, the mothers of two of the three children were known to be HIV positive and had not breast-fed their babies, ruling out mother-to-child transmission. The mother of the third child was not known to be positive, but a great aunt who cared for the child was.

The team found that the only way the children could have been infected was through pre-chewed food from caregivers who were bleeding from the mouth at the time. These findings may explain reported cases of later HIV transmission in infants, which had previously been attributed to breast feeding.

Researchers warn that until this route of transmission is studied further, HIV-positive caregivers should not pre-chew food for infants.