Epidemic

Lore & Background

The term epidemic derives from a word form attributed to Homer's Odyssey, which later took its medical meaning from the Epidemics, a treatise by Hippocrates. Before Hippocrates, variants had meanings similar to 'indigenous' or 'endemic'. Thucydides' description of the Plague of Athens is considered one of the earliest accounts of a disease epidemic. By the early 17th century, the terms endemic and epidemic referred to contrasting conditions of population-level disease, with the epidemic described as 'hapning in some region, or countrey, at a certaine time, ....... producing in all sorts of people, one and the same kind of sicknesse'.

Reader's Guide

Epidemics are generally caused by several factors including a change in the ecology of the host population, a genetic change in the pathogen reservoir, or the introduction of an emerging pathogen. An epidemic occurs when host immunity to an established or novel pathogen is suddenly reduced below that found in the endemic equilibrium and the transmission threshold is exceeded. The declaration of an epidemic usually requires a good understanding of a baseline rate of incidence; epidemics for certain diseases, such as influenza, are defined as reaching some defined increase in incidence above this baseline. A few cases of a very rare disease may be classified as an epidemic, while many cases of a common disease (such as the common cold) would not. The term can also be used for non-communicable health issues such as obesity. The United States Centers for Disease Control and Prevention defines epidemic broadly as 'an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area.' The term 'outbreak' can also apply, but is usually restricted to smaller events.

Did You Know?

• The term epidemic derives from a word form attributed to Homer's Odyssey.
• Thucydides' description of the Plague of Athens is considered one of the earliest accounts of a disease epidemic.
• The United States Centers for Disease Control and Prevention defines epidemic as 'an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area.'
• The term can also be used for non-communicable health issues such as obesity.