Children attending daycare also share ‘good’ germs
Socialization at an early age helps children develop greater diversity in their microbiomes, according to an analysis of the transmission of gut bacteria from child to child.
StockPlanets/Getty Images
An analysis has found that a large part of a baby’s developing microbiota comes from their peers in nursery, even after only one month of attendance.
The study, published today NatureAnalyzed the gut microbiome of infants during the first year of nursery. The amount of microorganisms transmitted between infants increased throughout the year. After four months, babies in the nursery already share 15–20% of their microbial species.
“This was more than the proportion of all the microbes they had received from the family from birth to that point,” says Nicola Segatta, a microbiologist at the University of Trento in Italy.
On supporting science journalism
If you enjoyed this article, consider supporting our award-winning journalism Subscribing By purchasing a subscription, you are helping ensure a future of impactful stories about the discoveries and ideas shaping our world today.
Some changes in babies’ microbiomes will be due to their diet in the nursery, but studies show that transmission of microbial strains between infants is widespread during the first year of nursery, and point to social interaction at this stage. Building a diverse, healthy microbiomeSegata adds.
bug transmission
While the fetus is still in the uterus, its microbiome is thought to be non-existent in healthy pregnancies, but it begins to develop rapidly after birth, primarily microbial transmission from mother. Research has shown that People who live together begin to share microbial strains. But, how the developing microbiota changes over the first few years of life has not been well studied.
To fill the knowledge gap, Segata and colleagues examined the microbiomes of 43 infants who were an average age of 10 months at the start of the study. They followed them before, during, and after they attended their first year of nursery in Trento, Italy.
“We enrolled children who were meeting for the first time on their first day of day care,” Segata says. “This is a time frame in which their gut is more prone to receiving stress from other babies and adults, because the immune system is not well trained yet.”
The team analyzed stool samples from the infants as well as 10 nursery workers and individuals living in the same households as the children: 39 mothers, 30 fathers, 7 siblings, 3 dogs and 2 cats.
Once the infants started nursery, the researchers continued taking samples every week until the Christmas holidays, and for some infants, this continued until July. Follow-up samples from all participants were taken in July and one year after the study began.
microbial richness
The analysis revealed that widespread microbiome transmission from child to child occurred just one month after infants started nursery, which continued to increase throughout the nursery year. If a child has a sibling, they receive more microbes from the sibling than from their parent, they have a more diverse microbiota overall, and they receive fewer bacterial strains from nursery mates.
The study also mapped the transmission of individual microbial species between individuals. gives an example of what happened with a type of bacteria called Segata. akkermansia muciniphila. “We have an example of stress spreading from a mother to an infant. The child in day care then passed it on to another child, who passed it on to both of their parents.”
There were also indications that bacterial strains were exchanged between pets and infants. “Interestingly, this was only for infants, not adults. So perhaps there are more ‘intimate’ interactions with infants and pets,” says Segata.
However, the most serious impact on the microbiota in infants came from the use of antibiotics. Antibiotic treatment during the first year of life severely reduced the number of bacterial strains in the infants’ gut microbiota, but this was rapidly improved by the widespread influx of fresh strains.
“It was surprising for me to see how mothers also acquired bacteria from other families through their children,” says María Carmen Collado, a food biotechnologist at the Institute of Agrochemistry and Food Technology in Valencia, Spain.
“I think this is a really cool piece of work that fills the gap in knowledge about the transmission of the microbiome,” says Collado. “I think this is going to open up new possibilities, not only with respect to the microbiome but also with our understanding of how pathogens spread.”
long term health effects Exposure to other microbial strains in the nursery has not been found to have any effect on the gut microbiome of infants. It is probably a combination of Diet and lifestyle Segata says this maintains bacterial diversity in the gut microbiota in later life. Given that the newly acquired strains were still present at the end of the year, it is possible that they persisted into adulthood.
“Maybe in 20 years, we’ll find that people still have their friends at day care to thank for the germs they got while they were there,” he says.
This article is reproduced with permission and was first published On 21 January 2026.
It’s time to stand up for science
If you enjoyed this article, I would like to ask for your support. scientific American He has served as an advocate for science and industry for 180 years, and right now may be the most important moment in that two-century history.
i have been one scientific American I’ve been a member since I was 12, and it’s helped shape the way I see the world. Science Always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does the same for you.
if you agree scientific AmericanYou help ensure that our coverage focuses on meaningful research and discovery; We have the resources to report on decisions that put laboratories across America at risk; And that we support both emerging and working scientists at a time when the value of science is too often recognised.
In return, you get the news you need, Captivating podcasts, great infographics, Don’t miss the newsletter, be sure to watch the video, Challenging games, and the best writing and reporting from the world of science. you can even Gift a membership to someone.
There has never been a more important time for us to stand up and show why science matters. I hope you will support us in that mission.
