Eradication of infectious diseases
Eradication is the reduction of an infectious disease's prevalence in the global host population to zero. It is sometimes confused with elimination, which describes either the reduction of an infectious disease's prevalence in a regional population to zero, or the reduction of the global prevalence to a negligible amount. Further confusion arises from the use of the term eradication to refer to the total removal of a given pathogen from an individual (also known as clearance of an infection), particularly in the context of HIV and certain other viruses where such cures are sought.Selection of infectious diseases for eradication is based on rigorous criteria, as both biological and technical features determine whether a pathogenic organism is (at least potentially) eradicable. The targeted organism must not have a non-human reservoir (or, in the case of animal diseases, the infection reservoir must be an easily identifiable species, as in the case of rinderpest), and/or amplify in the environment. This implies that sufficient information on the life cycle and transmission dynamics is available at the time an eradication initiative is programmed. An efficient and practical intervention (e.g., a vaccine or antibiotic) must be available to interrupt transmission of the infective agent. Studies of measles in the pre-vaccination era led to the concept of the Critical community size, the size of the population below which a pathogen ceases to circulate. Use of vaccination programmes before the introduction of an eradication campaign can reduce the susceptible population. The disease to be eradicated should be clearly identifiable, and an accurate diagnostic tool should exist. Economic considerations, as well as societal and political support and commitment, are other crucial factors that determine eradication feasibility.Eight attempts have been made to date to eradicate infectious diseases: two successful programs targeting smallpox and rinderpest; four ongoing programs targeting poliomyelitis, yaws, dracunculiasis and malaria; and two former programs targeting hookworm and yellow fever. Five more infectious diseases have been identified as of April 2008 as potentially eradicable with current technology by the Carter Center International Task Force for Disease Eradication—measles, mumps, rubella, lymphatic filariasis and cysticercosis.