major
global, national, worldwide
growing
deadly, devastating
cholera, flu, foot-and-mouth, typhoid, etc.
crack, heroin, etc.
silent

become
combat, fight
cause

break out, occur, strike (sth)
A typhus epidemic struck in the winter of 1919–20.

spread, sweep (sth)
the flu epidemic sweeping the country

during an/the epidemic, in an/the epidemic
Over fifty people died during the flu epidemic last winter.

epidemic of
an epidemic of cholera

reach epidemic proportions
Marriage breakdown in the West has reached epidemic proportions.

Epidemic is used with these nouns:
proportion