Microbiologist Professor Frederic Bushman, co-director of the Center for Research on Coronaviruses and Other Emerging Pathogens at the University of Pennsylvania, has just led a study into the effect of breastfeeding on viruses in infants’ guts.

He says: “It’s well known that the human gut microbiome influences health and disease, but the human virome – the populations of viruses in humans – are less well studied. We know breastfeeding plays a key role in the interaction between babies and the microbial environment, and our new work discloses that breastfeeding strongly modulates the virome.

“At birth, there are usually no viruses in the guts of healthy infants. Over time, the gut becomes colonised by bacteria and viral populations. Upon delivery, babies have little or no colonisation, but by one month of life populations of viruses and bacteria are well developed, with numbers of viruses reaching a billion per gram of gut contents.

Most of the first wave of viruses in infants grow in the first bacteria to colonise the gut – later, viruses that infect humans appear, some of which can sicken infants. Breastmilk modulated this second phase, suppressing the accumulation of potentially pathogenic viruses.

“These findings tell us that even small amounts of breastmilk mixed with baby formula can provide a protective effect against pathogenic viruses in infants. The more breastfeeding the better, but this work shows that if exclusive breastfeeding isn’t feasible, then partial breastfeeding is much better than no breastfeeding.

“There’s considerable evidence that breastmilk helps suppress gastrointestinal disorders and intestinal viruses. These findings will help guide strategies for the prevention of early gastrointestinal diseases, and encourage mothers that are able to feed babies breastmilk to do so, even when mixed with formula.”