Turn your students into epidemiologists as they spend their class time searching for the source of an artificial epidemic. Your job is to hide the commonly used, non-pathogenic yeasts in your classroom. Your students, knowing that yeasts produce catalase (which breaks down hydrogen peroxide into oxygen and water), can sample various locations as they attempt to track down the source of the microorganisms. This lab lends itself to an almost infinite number of variations, and will likely help your students appreciate the work of public health officials. Developed by Edward Alcamo. Includes materials for 30 students and a teacher’s guide with background information. Grades 9–12.