RNA viruses provide unique insights into the patterns and processes of evolutionary change in real time. The study of viral evolution is especially topical given the growing awareness that emerging and re-emerging diseases (most of which are caused by RNA viruses) represent a major threat to public health. However, while the study of viral evolution has developed rapidly in the last 30 years, relatively little attention has been directed toward linking work on the mechanisms of viral evolution within cells or individual hosts, to the epidemiological outcomes of these processes. This novel...