The study, published in Nature Communications, shows that phage therapy—the use of tiny viruses to kill bacteria without harming people—could help reduce recurrent infections, which happen when the bacteria responsible for UTIs “hide” in the tissue of the bladder.

UTIs are one of the world’s most common infections, with around 400 million cases each year. They can be painful and disruptive, and for many people, the infection can return after taking a course of antibiotics.