Mothers infected with HIV are typically advised to exercise caution when breastfeeding because breast milk has long been suspected as a vehicle for transmission. But a new study published in the journal PLoS Pathogens suggests just the opposite: that breast milk may actually kill the virus, as well as offer protection from transmission, reports New Scientist.The study, conducted by researcher Angela Wahl at the University of North Carolina at Chapel Hill, was performed on mice engineered with human immune systems. The mice were fed breast milk laced with both HIV particles and virus-infected cells, yet they did not contract the virus. In fact, not only did breast milk protect against transmission, but it seemed to actively destroy the virus.MORE FROM MNN: Can Cord Blood Transplant Provide HIV Cure?“We have shown that milk has an intrinsic innate ability to kill HIV,” said J. Victor Garcia, who supervised the work.Although the exact component that kills the virus is currently unknown, the discovery offers hope that a cure for HIV may have been hiding in plain sight all along: in mother’s milk. The next step is to isolate the mystery ingredient and see if it can be manufactured into a general treatment for preventing HIV transmission.The findings are certainly good news for mothers infected with HIV, though until more research is performed mothers are advised to remain cautious. (The fact that the study was done on mice is reason enough to exercise patience.) Also, the study is sure to generate controversy because it flies in the face of what has long been believed about breast milk’s role in HIV transmission.According to World Health Organization data, around 15 percent of children breastfed by HIV-positive mothers contract the virus. The fact that the number is so low bodes well for the theory that breast milk is not the conduit for transmission. But until more research is conducted, that number should also be considered too high for mothers to take the risk.MORE FROM MNN: What are HIV Symptons?Because of the multifarious health benefits of breast milk, the World Health Organization still recommends that all mothers breastfeed their children for at least 12 months — but that advice comes with a caveat for HIV-positive mothers. HIV-positive mothers and their infants must be put on a course of antiretroviral medications first.Researchers will also need to ask: Even if breast milk is shown to prevent HIV transmission, how then do those 15 percent of children contract it? It’s possible, of course, that suckling babies can still contract the virus from exposure to the mother’s blood via cuts on the nipple, or from excessive sucking. But it’s impossible to know for certain until further research is conducted.