An occurrence of disease cases in a particular place, population, or period that is greater than expected or linked by a common source or transmission event.
Outbreaks are often used to describe clusters of infectious disease in settings such as schools, hospitals, communities, workplaces, or events. Public health investigations may examine when cases occurred, where they occurred, and how people were exposed.
The distinction between an outbreak and an epidemic is not always absolute, and terminology can vary according to context.
QUICK FACT
An outbreak can involve a small number of cases if the expected number is normally zero, for example, a single case of a disease that has been eliminated from a particular area.
COMMONLY CONFUSED WITH
Epidemic: a broader term for occurrence above the expected level in a population; an outbreak often describes a more localized event.
SEE ALSO