A total of 232 previously unknown viral families have been detected in the intestines of infants.
- The presence of 10,021 viruses has been found in the dirty diapers of healthy one-year-old children.
- More than 200 species of bacteriophages, inherited viruses that help maintain the balance of the intestinal microbiota, were unknown.
- The development of chronic diseases, such as asthma, could be linked to a dysregulation of the immune system, which “has not been trained correctly”.
“The gut microbiota is formed in early childhood and influences the maturation of the immune system, thereby protecting against chronic diseases, such as asthma and diabetes, later in life,” indicated researchers from the University of Copenhagen (Denmark). Recently, they have identified thousands of viruses present in the intestines of babies. To reach this discovery, they carried out a study, the results of which were published in the journal Nature Microbiology.
“More than 200 viral families had not yet been described”
As part of this work, the scientists analyzed and mapped the contents of the diapers, ie the stools, of 647 Danish children, in good health, aged one year. They were interested in the presence of “bacteriophages”, namely viruses transmitted by parents and specific to bacteria. They develop independently of external factors.
“We found an exceptional number of unknown viruses in the stools of these babies. Not only thousands of new virus species, but to our surprise, more than 200 viral families had not yet been described. This means that, from an early age, healthy children show an extreme diversity of intestinal viruses, which probably have a major impact on the development of various diseases”, explained Dennis Sandris Nielsen, author of the research, in a statement.
Bacteriophages, allies against diseases?
According to the results, 90% of the viruses discovered by the team are bacteriophages that do not attack baby cells, which means that they do not cause disease. “Bacteriophages are largely responsible for the formation of bacterial communities and their function in our intestinal system. (…) It appears that bacteriophages help maintain the balance of the intestinal microbiome by controlling individual bacterial populations, which guarantees that there is not just one bacterial species in the ecosystem”, said Shiraz Shah, co-author of the study.
The remaining 10% of viruses found in infant stool were eukaryotes, which use human cells as hosts. “Interestingly, all children carry 10 to 20 of these types of viruses that infect human cells. So there is a constant viral infection that apparently does not make them sick. We only know very little about what’s actually involved. I think they’re important for training our immune system to recognize infections later. But they may also be a risk factor for diseases that we don’t know about. have not yet discovered”, added Dennis Sandris Nielsen, a professor who participated in the work.
Some viruses are introduced by environmental elements later
For the time being, scientists have not yet discovered the origin of the many viruses present in children. “Our gut is sterile until birth. During birth, we are exposed to bacteria from the mother and the environment. It is likely that some of the first viruses accompany these initial bacteria, while many others are introduced later by dirty fingers, pets, dirt that children put in their mouths and other elements of the environment”, specified Dennis Sandris Nielsen.
According to the researchers, the development of chronic diseases could be caused by a dysregulation of the immune system, which “was not trained properly”. “Therefore, if we learn more about the role bacteria and viruses play in a well-trained immune system, we can hopefully be able to stave off many of the chronic diseases that affect so many people today.” , concluded Shiraz Shah.