Prevalence and incidence


February 18th, 2015

Prevalence is a measurement of the state of health of a population within a particular period of time. For a given disease, it is calculated by referring to the targeted population the number of cases of disease known at a given time within this population. Prevalence is a proportion generally expressed as a percentage.

Prevalence should not be confused with incidence. Incidence only takes into account the number of new cases per year, while prevalence is based on the total number of cases present, i.e., those already present, plus those that are incidental. Thus, prevalence is always superior to incidence.

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