Researchers uncover hidden gut virus tied to colorectal cancer

A Danish-led study identifies a previously unknown bacteriophage inside the gut bacterium Bacteroides fragilis that is more common in individuals with colorectal cancer, a pattern replicated in independent cohorts from Europe, the US, and Asia. While the virus–bacterium interaction may help explain cancer risk and could become a future stool-based screening marker, causality is not yet established, and researchers are pursuing further experiments in gut models, tumor tissue, and animal studies.