Critical_community_size
Critical community size
Minimum size of a closed population within which a pathogen can persist indefinitely
The critical community size (CCS) is the minimum size of a closed population within which a human-to-human, non-zoonotic pathogen can persist indefinitely.[1]
When the size of the closed population falls below the critical community size level, the low density of infected hosts causes extinction of the pathogen.[2] This epidemiologic phenomenon was first identified during measles outbreaks in the 1950s.[1]
The critical community size depends on:[citation needed]
- Speed of transmission
- How long until a person who has recovered remains immune
- Fatality rate
- Birth and death rate in the general population
