The researchers are calling the virus “crAssphage.” Once they figured out where to find it, crAssphage turned up so often that the study authors say more than half of all people are likely walking around with it in their bellies. The fact that the virus is so common means it’s likely very old—maybe even as old as the human race, the authors suggest.   MORE: Training For A Tri Commonly Leads To Pelvic Floor Disorders “Our intestines are full of bacteria, and we need them to help digest food and adsorb nutrients,” explains study coauthor Robert Edwards, PhD. He says phages like crAssphage control the growth of bacteria by infecting them and killing them, just like wolves control the populations of hares and deer.   Two of the most common bacteria in the intestines are called Bacteroides and Firmicutes, Edwards explains, adding that past research suggests the ratio of these two may have important implications for human health—especially when it comes to obesity and diabetes. Because crAssphage may infect both of these types of bacteria, it could also have a part in the development of those diseases.   “We don’t know yet what the role of crAssphage is,” Edwards stresses. “But a widespread virus like this one is likely to be implicated in diseases commonly associated with the intestine.”   Why should any of this matter to you? Identifying crAssphage could be a very important first step when it comes to developing new gut bacteria-based medical treatments that could one day be used to help diabetics and others with intestine-related health issues, Roberts explains. Unfortunately, those types of gut-based treatments are still about 5 years away from lab or clinical trials, he says. (In the meantime, check out our comprehensive guide to living with and preventing diabetes.)  “There are lots of researchers trying to define the precise role of bacteria in these diseases,” Edwards adds. “But we don’t truly understand what [these bacteria] are doing at the moment.”  MORE: The Happy Effect Exercise Has On Your…Gut Bacteria?