outbreak

noun

1. a sudden breaking out or occurrence; eruption: the outbreak of war.
2. a sudden and active manifestation: an outbreak of hives.
3. an outburst: an outbreak of temper.
4. an insurrection, revolt, or mutiny.
5. a public disturbance; riot.

noun

1. a sudden, violent, or spontaneous occurrence, esp of disease or strife

n.“eruption” (of disease, hostilities, etc.), c.1600, from out + break (v.). Outbreak was a verb in Middle English (c.1300).