noun

a widespread occurrence of an infectious disease in a community at a particular time.

a flu epidemic

outbreak,plague,scourge,infestation,widespread illness/disease,pandemic,epizootic,recrudescence,boutade

adjective

of the nature of an epidemic.

epidemic diseases

rife,rampant,widespread,wide-ranging,extensive,sweeping,penetrating,pervading,global,universal,inescapable,ubiquitous,prevalent,predominant,endemic,pandemic,epizootic