Definition of Pandemic, Endemic, Epidemic and Syndemic

Pandemic (from Gree pan "all" and demos "people") is a disease epidemic that has spread across a large region, viz. multiple continents, or worldwide. A pandemic is an epidemic occurring on a scale that crosses international boundaries, usually affecting a large population.

Endemic (from Greek en "in, within" and demos "people") an infection is said to be endemic in a population when that infection is constantly maintained at a baseline level in a geographic area without external inputs.

Epidemic An epidemic (from Greek epi "upon or above" and demos "people") is the rapid spread of disease to a large population in given population within a short period of time.

A syndemic or synergistic epidemic is the aggregation of two or more concurrent or sequential epidemics or disease clusters in a population with biological interactions, which exacerbate the prognosis and burden of disease.