Critical community size

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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

See also[edit]


  1. ^ a b Bartlett, M. S. (1960). "The critical community size for measles in the United States". Journal of the Royal Statistical Society. Series A (General). 123 (1): 37–44. doi:10.2307/2343186. JSTOR 2343186.
  2. ^ Haydon, Daniel T; Cleaveland, Sarah; Taylor, Louise H; Laurenson, M Karen (2002). "Identifying reservoirs of infection: a conceptual and practical challenge". Emerging Infectious Diseases. 8 (12): 1468–1473. doi:10.3201/eid0812.010317. PMC 2738515. PMID 12498665.

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