This is a companion volume to Viral Infections of Humans: Epidemiology and Control. The apparent success of that book in bridging the gap between texts on basic microbiology and those on clinical infectious diseases led to editing this one on bacterial infections, the chapters of which are organized in exactly the same format of 12 units: introduction, historical background, methodology, biological characteristics of the organism, descriptive epidemiology, mechanisms and routes of transmission, pathogenesis and im­ munity, patterns of host response, control and prevention, unresolved problems, references, and suggested reading. The purpose of this book is to provide a description and understanding of the pathogenesis of infection and disease both within the community and within the individual. This is done in the belief that a variety of factors in both the external and the internal environment, and in the nature of the infectious agent, influence exposure, the development of infection, and the pattern of the host response. An understanding of the epidemiology and pathogenesis of these processes forms the basis for approaches to control and prevention. The first two chapters of this book deal with general epidemiological concepts and with surveillance.