Cluster (epidemiology)

A cluster refers to a grouping of health-related events that are related temporally and in proximity. Typically, when clusters are recognized, they are reported to public health departments in the local area. The epidemic of cholera which occurred in London in the 1850s is a classical example of a cluster. If clusters are of sufficient size and importance, they may be re-evaluated as outbreaks, as was the case with the example just given.