Endemic: A characteristic of a particular population, environment, or region. Examples of endemic diseases include chicken pox that occurs at a predictable rate among young school children in the United States and malaria in some areas of Africa. The disease is present in a community at all times but in relatively low frequency.
By contrast, there are the related terms "epidemic" and "pandemic":
- An epidemic is a sudden severe outbreak within a region or a group, as with AIDS in Africa or AIDS in intravenous drug users.
- A pandemic occurs when an epidemic becomes very widespread and affects a whole region, a continent, or the entire world.
The word "endemic" comes from the Greek "en-", "in" + "demos", "people or population" = "endemos" = "in the population." An endemic is in the people.
By contrast, "epi-" means "upon." An epidemic is visited upon the people. And "pan-" means "all." A pandemic affects all the people.