One of the functions of public health is to reduce the impact of emergency situations; hence the need to establish an early warning and response system. Community reactions to emerging and reemerging diseases, exposure to environmental risks, and potential terrorist acts are the factors that have that have mainly contributed to the instauration of warning systems based on mathematical models. Information is obtained from diverse sources (for example, laboratory data, sentinel physicians, or visits to particular websites). Once the data are gathered, and the situation provoking the alert is detected, control measures to reduce risks and minimize damage are taken at the earliest.