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In epidemiology, infectivity is the ability of a pathogen to establish an infection. More specifically, infectivity is the extent to which the pathogen can enter, survive, and multiply in a host. It is measured by the ratio of the number of people who become infected to the total number exposed to the pathogen.[1]

Infectivity has been shown to positively correlate with virulence, in plants. This means that as a pathogen's ability to infect a greater number of hosts increases, so does the level of harm it brings to the host.[2]

A pathogen's infectivity is different from its transmissibility, which refers to a pathogen's capacity to pass from one organism to another.[1]

See also[edit]


  1. ^ a b Oxford textbook of global public health (6th ed.). Oxford: Oxford university press. 2015. p. 1486. ISBN 978-0-19-966175-6.
  2. ^ Stewart, AD; Logsdon, JM; Kelley, SE (April 2005). "An empirical study of the evolution of virulence under both horizontal and vertical transmission". Evolution. 59 (4): 730–739. doi:10.1554/03-330. PMID 15926685. S2CID 924610.