There are a number of well-recognized physical hazards associated with running in mud obstacle races, but recent reports have also brought to light the infectious hazards that competitors may encounter. This case study contains actual data from two such infectious outbreaks: one that occurred following a mud run on a cattle ranch in Nevada in 2012, and the other after a mud run at Michigan International Speedway in 2013. The case is presented as a conversation between two fictional characters: “Sam,” a college senior, and her mother, a physician. Sam is planning to participate in a mud run and her mother is concerned, especially since she recently treated patients from one of the latest outbreaks. Using the information conveyed in the story, supplemented by a video of a mud run and a discussion of disease transmission, students are asked to decide what Sam should do. The case was originally written for a microbiology course, but it could also be used in other courses that cover the topics of disease transmission and epidemiology.