cHowever, people have never been sicker than average, and the vast majority of these viruses are harmless to humans. It just so happens that we’ve never done any research on this scale on everything that lives in our gut – and some of it ends up in our poop: 12,000 people in question come from 24 countries and work, published June 24 in the journal Nature Microbiology, consists of doing what is called a “metagenomic” analysis, that is, looking at the genes as a whole, but without breaking them down one by one.

The 54,118 types of viruses in question here, represented by about 190,000 viral genomes, are largely phages, that is, viruses that feed on bacteria. This is why these viruses are not dangerous to humans: they cannot attack our cells, preferring bacteria over them. They are part of the natural ecosystem of the human body – they are also called microorganisms.

For microbiologists, this discovery is also important for another reason: databases of “our” microorganisms have previously identified quite a few phages. There is still a lot of ground to be cleared about this topic: it is estimated that more than 70% of microbes discovered so far cannot be grown in the laboratory.

But for infectious disease experts, the sudden interest in phages has another meaning: An old concept in biology called phage therapy, or phage therapy, suggests that viruses can be used to “attack” bacterial infections. The theory has been around for a hundred years, and was sidelined by the success of antibiotics in the mid-20th century. However, with the development towards bacteria increasingly resistant to antibiotics, interest has recently emerged in further research on phages. In other words, perhaps our intestines hold the secrets of the weapons of the future against diseases of the future …