The story of infectious diseases—their causes, detection, control, treatment, and prevention—are fundamental to public health’s story. Basic public health concepts, such as incidence, prevalence, case fatality rate, herd immunity, and so forth, were developed through study of infectious diseases. The terms epidemic, pandemic, and endemic are fundamental to public health methods. Instances in which infectious diseases have been identified and controlled are among the most important of public health’s successes and include cholera, smallpox, tuberculosis, polio, and so many others. The public health role in developing vaccines and the success of immunizations in controlling many infectious diseases cannot be overestimated. These public health successes have had a major impact on morbidity and mortality, historically and in the present. The public health infrastructure around control and prevention of infectious diseases, as well as the methods developed, are essential to the health of Americans.