A century after they were discovered killing diarrhea-causing bacteria in the feces of World War I soldiers, the viruses known as bacteriophages, or simply phages, are drawing new attention for the role they might play within the human body. Phages have been found most everywhere, from oceans to soils. Now, a study suggests that people absorb up to 30 billion phages every day through their intestines. Though where those viruses end up is unclear, those data and other recent studies have some scientists wondering whether a sea of phages within the human body—a “phageome”—might play a key role in our physiology, perhaps by regulating our immune system.
