“Endemic” is in danger of losing its core meaning through confusion with “epidemic.” An endemic condition is one characteristic of a particular region, population, or environment: “sore thumbs are endemic among teen text-messagers.” A condition need not affect a majority or even a very large number of people in a population to be endemic. In biology, an endemic disease is one that is maintained locally without the need for outside influence: “Cholera is endemic in Kolkata.” It keeps recurring there, but still only a small minority of the population gets cholera.
An epidemic condition is widespread, rampant: “ Overindulgence in fatty foods is epidemic throughout the world.” The dominance of the noun “epidemic” (“the threat of a flu epidemic”) may make people reluctant to use it as an adjective (“flu may become epidemic”) but both uses are legitimate. It’s best to stick with “epidemic” unless you have a specific need for the technical term “endemic.”
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