Tuberculosis presents a significant public health challenge. In this teaching case, medical students are given information about four cases of active tuberculosis that occurred over a short period of time in residents of a homeless men’s shelter. The students then walk through the steps that a local health department takes to identify and screen those individuals at risk for transmission of tuberculosis during an outbreak. During this process, they learn skills in epidemiology (such as defining "epidemic" and distinguishing uses for incidence and prevalence) as well as in population-based prevention of tuberculosis. Finally students discuss health policy as it relates to the control and prevention of tuberculosis.