Epidemic
From the Greek "epi-", "upon" + "demos", "people or population" = "epidemos" = "upon
the population".The occurrence of more cases of disease or other health condition than
expected in a given area or among a specific group of persons during a particular
period. Usually, the cases are presumed to have a common cause or to be related to
one another in some way. In epidemiology, an epidemic occurs when new cases of a
certain disease, in a given human population, and during a given period, substantially
exceed what is expected based on recent experience.The number of cases indicating
the presence of an epidemic varies according to the agent, size, and type of population
exposed, previous experience or lack of exposure to the disease, and time and place
of occurrence.
See also: Endemic; Pandemic.
Note: The definitions of outbreak, epidemic, and pandemic, given in this Glossary, are
the classical epidemiologic definitions. However, as overuse of these terms not only in
professional literature, but also in the media, has lead to ambiguity in the perception of
their meaning by audiences. In this respect, when using the terms, one must take care
to clarify the specifics of the respective situation in terms of geographic spread,
severity and case-fatality ratio.