Emerging infectious disease

An emerging infectious disease (EID) is an infectious disease whose incidence has increased in the past 20 years and threatens to increase in the near future. EIDs include diseases caused by a newly identified microorganism or newly identified strain of a known microorganism (e.g. SARS, AIDS); new infections resulting from change or evolution of an existing organism (e.g. influenza), a known infection which spreads to a new geographic area or population (e.g. West Nile virus), newly recognized infection in an area undergoing ecologic transformation, and pre-existing and recognized infections reemerging due to drug resistance of their agent or to a breakdown in public health (e.g. tuberculosis).

Mechanisms of emergence and reemergence

 * Microbial adaption; e.g. genetic drift and genetic shift in Influenza A
 * Changing human susceptibility; e.g. mass immunocompromisation with HIV/AIDS
 * Climate and weather; e.g. diseases with zoonotic vectors such as West Nile Disease (transmitted by mosquitoes) are moving further from the tropics as the climate warms
 * Change in human demographics and trade; e.g. rapid travel enabled SARS to rapidly propagate around the globe
 * Economic development; e.g. use of antibiotics to increase meat yield of farmed cows leads to antibiotic resistance
 * Breakdown of public health; e.g. the current situation in Zimbabwe
 * Poverty and social inequality; e.g. tuberculosis is primarily a problem in low-income areas
 * War and famine
 * Bioterrorism; e.g. 2001 Anthrax attacks
 * Dam and irrigation system construction; e.g. malaria and other mosquito borne diseases