Book excerpt: Zoonotic diseases represent one of the leading causes of illness and death from infectious disease. Defined by the World Health Organization, zoonoses are "those diseases and infections that are naturally transmitted between vertebrate animals and man with or without an arthropod intermediate." Worldwide, zoonotic diseases have a negative impact on commerce, travel, and economies. In most developing countries, zoonotic diseases are among those diseases that contribute significantly to an already overly burdened public health system. In industrialized nations, zoonotic diseases are of particular concern for at-risk groups such as the elderly, children, childbearing women, and immunocompromised individuals. The Emergence of Zoonotic Diseases: Understanding the Impact on Animal and Human Health, covers a range of topics, which include: an evaluation of the relative importance of zoonotic diseases against the overall backdrop of emerging infections; research findings related to the current state of our understanding of zoonotic diseases; surveillance and response strategies to detect, prevent, and mitigate the impact of zoonotic diseases on human health; and information about ongoing programs and actions being taken to identify the most important needs in this vital area.