A widespread outbreak of an infectious disease; many people are infected at the same time.
Outbreak of infectious disease affecting large numbers of people at the same time. A widespread epidemic that sweeps across many countries (such as the Black Death in the late Middle Ages) is known as a pandemic.

ETYM French pestilence, Latin pestilentia. Related to Pestilent.
A pernicious evil influence.
1. A contagious or infectious epidemic disease that is virulent and devastating; especially; bubonic plague.
2. Something that is destructive or pernicious.