Low-Incidence, High-Consequence Pathogens

Infectious diseases that have epidemic or pandemic potential and spread rapidly through a population within a short time are an ongoing public health concern in industrialized and developing countries. Frequent exposure to infectious sources (e.g., food, infected animals, and vectors) or a high rate of person-to-person spread facilitates spread of these diseases. Foodborne illnesses and seasonal influenza are notable examples. These diseases typically are associated with high rates of illness and substantial societal and economic cost but relatively low rates of death in otherwise healthy persons. Other infectious diseases, in contrast, may occur infrequently but are associated with high rates of death. The low incidence of some of these diseases reflects effective public health prevention measures, such as vaccinations. For a select group of zoonotic infectious diseases with high death rates, the low incidence reflects infrequent spillover from an animal reservoir into humans. Often, humans represent a dead-end host for these pathogens, and person-to-person transmission is rare if appropriate infection control practices are followed. Many of the pathogens highlighted in the current issue of Emerging Infectious Diseases can collectively be described as low-incidence, high-consequence pathogens. Selected diseases caused by these pathogens are described below.