Epidemic
From Free net encyclopedia
In epidemiology, an epidemic (from Greek epi- upon + demos people) is a disease that 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 epizootic is 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 locale (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 malaria in 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 plague epidemic of Medieval Europe known as the "Black Death", the Great Influenza Pandemic concurring with the end of World War I, and the current AIDS epidemic, 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 societal problems, for example, in discussions of mental illness or drug addiction.
See also
ca:Epidèmia cs:Epidemie da:Epidemi de:Epidemie es:Epidemia eo:Epidemio eu:Izurrite fr:Épidémie gl:Epidemia id:Wabah it:Epidemia lt:Epidemija nl:Epidemie ja:伝染病 no:Epidemi nn:Epidemi pl:Epidemia pt:Epidemia ru:Эпидемия sq:Epidemia simple:Epidemic sk:Epidémia sl:Epidemija sv:Epidemi zh:流行病