Epidemic

In epidemiology, an epidemic (from Greekepi- upon + demos people) is a diseasethat appears as new cases in a given human population, during a given period, at a rate that substantially exceeds what is "expected," based on recent experience (the number of new cases in the population during a specified period of time is called the "incidence rate"). (An epizooticis the same thing but for a nonhuman population.)

Defining an epidemic can be subjective, depending in part on what is "expected." An epidemic may be restricted to one local (an outbreak), more general (an "epidemic") or even global (pandemic). Because it is based on what is "expected" or thought normal, a few cases of a very rare disease like rabies may be classified as an "epidemic," while many cases of a common disease (like the common cold) would not.

Common diseases that occur at a constant but relatively high rate in the population are said to be "endemic." An example of an endemic disease is malariain some parts of Africa(for example, Liberia) in which a large portion of the population is expected to get malaria at some point in their lifetimes.

Famous examples of epidemics include the bubonic plagueepidemic of MedievalEuropeknown as the Black Death, the Great Influenza Pandemicconcurring with the end of World War I, and the current AIDSepidemic, which some also consider to be of pandemic proportions.

Types of Epidemics

Epidemics are classified into multiple types based on their origin and pattern of transmission. Epidemics can involve a single exposure, multiple exposures, or a continuous exposure to the disease-causing agent. The disease involved in an epidemic can be transmitted by a vector, from person to person, or from a common source such as contaminated water.

Non-biological usage

The term is often used in a non-biological sense to refer to widespread and growing societalproblems, for example, in discussions of mental illnessor drug addiction.

See also

• Endemic
• Epidemiology
• Pandemic
• Mathematical modelling in epidemiology
• List of epidemicsbs:Epidemija

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It uses material from the http://en.wikipedia.org/wiki/Epidemic Wikipedia article Epidemic.