Outbreak (noun)

1. A sudden occurrence or explosion of something undesirable, such as disease, violence or war.
2. A sudden increase in the incidence of a disease in a particular place or group of people.
3. The start of something dangerous or unpleasant, such as a conflict or a riot.
4. A sudden emergence of something, such as a fire or a leak.
5. A sudden start or onset of something, such as a storm or a hurricane.

Origin:

From out- +‎ break, meaning sudden occurrence, explosion.

Examples:

1. The government is doing everything possible to contain the outbreak of the virus.
2. There was an outbreak of violence on the streets after the announcement of election results.
3. The health authorities are investigating the cause of the outbreak of the disease in the region.
4. The police were called in to control the outbreak of riots in the city.
5. The sudden outbreak of a storm caught the residents of the town by surprise.