Scientists with the Defense Advanced Projects Research Agency (DARPA) are working on a program that someday could allow persons to predict when they would become sick following exposure to an illness. The Prometheus program aims to identify “molecular biomarkers” that would determine whether a person would contract a sickness, within fewer than 24 hours after exposure to a pathogen. Researchers hope that such early diagnoses would help health-care providers offer treatment and remedies in a more timely and effective manner. Prometheus also could identify carriers of an illness who still could spread it, even if they do not become sick themselves.