California, US,21 August 2025
Study Hints at Bird Flu Breast Milk Risk:
As H5N1 bird flu continues to spread among mammals, a new study has raised the possibility that nursing parents infected with the virus could transmit it to their babies through breast milk, prompting a new area of research for public health officials.
A recent, pre-print study has brought a new potential concern to the ongoing avian influenza (H5N1) outbreak, suggesting that the virus might be capable of infecting human breast tissue and, in turn, being transmitted through breast milk.
The findings, which have not yet been peer-reviewed, raise important questions for public health and have prompted a new round of research into the virus’s behavior in humans.
The study was inspired by the 2024 outbreak of H5N1 in dairy cows, where the virus was found to be present at high levels in the animals’ udders and milk. Researchers from the University of California, San Diego, sought to understand whether a similar mechanism could exist in humans. They found that human mammary glands contain a specific type of sugar molecule, called sialic acid receptors, that the H5N1 virus can use to infect cells. The presence of these receptors in human breast tissue indicates a potential pathway for infection.
* A New Avenue for Concern
The findings are particularly noteworthy because H5N1 has been shown to infect other mammals, including dairy cattle, cats, and wild animals, and has been detected in the unpasteurized milk of infected cows. While there is no evidence to date of a human baby being infected with H5N1 through breast milk, the research provides a biological basis for a potential transmission route. It adds a layer of complexity to the public health guidance around the virus, which has primarily focused on avoiding contact with infected animals and their products.
* Ongoing Research and Current Guidance
The Centers for Disease Control and Prevention (CDC) and other public health authorities are actively monitoring the situation. While the risk of human-to-human transmission of H5N1 is currently considered low, the virus’s ability to infect new species, and now, potentially, new human organs, is a cause for vigilance.
Researchers are now investigating whether the H5N1 virus can survive in breast milk and how it might get into the mammary glands and milk in the first place. For now, the CDC encourages women to continue to breastfeed or provide breast milk, noting that breast milk contains antibodies that may help protect a baby from infection.
However, they advise that women who are ill should consult with a healthcare professional for specific guidance on their situation. The new study serves as a crucial reminder that as the H5N1 virus continues to evolve, so must our understanding of its potential pathways for transmission and its public health risks.
