Epidemic

a. [Gr. ἐπιδήμος, among the people; Fr. épidémique.] 1. Common to, or affecting, a whole people, or a great number in a community; prevalent; general. It was the epidemical sin of the nation. Burnet. 2. Generally prevailing; affecting great numbers; as, epidemic rage; an epidemic evil. Epidemic disease, one of which the cause acts upon numbers of people at the same time from its wide diffusion, as through meteorological influences, &c. Thus we speak of an epidemic fever, an epidemic catarrh. See ENDEMIC.

n. (Med.) A disease which, arising from a wide-spread cause, affects numbers of persons at the same time.