Refers to a concentration of people with the same infections in the same area at the same time.

The World Health Organization uses the following categories to describe the transmission patterns of COVID-19:

  1. sporadic cases which refer to a small number of cases (one or more) that are either imported or detected locally
  2. clusters of cases which are grouped in time, geographic location, and or by common exposures
  3. community transmission which refers to larger outbreaks of local transmission

TIP: Outbreak and cluster are often confused. According to the US Center for Disease Control, an outbreak carries the same definition as an epidemic but is often used for a more limited geographic area. A cluster refers to a collection of cases grouped in place and time that are suspected to be greater than the number expected, even though the expected number may not be known.


Epidemiology Infectious Disease Transmission


WHO (World Health Organisation)COVID-19Community transmission