epidemic

(especially of medicine) of disease or anything resembling a disease; attacking or affecting many individuals in a community or a population simultaneously

Common to, or affecting at the same time, a large number in a community; -- applied to a disease which, spreading widely, attacks many persons at the same time; as, an epidemic disease; an epidemic catarrh, fever, etc. See Endemic.

a widespread outbreak of an infectious disease; many people are infected at the same time

An epidemic disease.