Studying complex diseases is like trying to solve a massive jigsaw puzzle with a blank box cover and who knows how many missing pieces. Scientists now realize that human genes form the borders of many disorders. But it turns out that the picture can’t be filled in without considering microbes, especially the bacteria and viruses that make the human body home.
Four years ago, evolutionary geneticist Vicente Pérez-Brocal found himself trying to complete the Crohn’s disease puzzle. As a member of a research group headed by Andrés Moya at the University of Valencia in Spain, Pérez-Brocal was tasked with determining if viruses fit into the picture.