[Prevalence and incidence].
The first requirement in any epidemiological study of a disease is to measure the proportion of the population affected. This is usually expressed in terms of "prevalence" or "incidence", but these two words are often used indiscriminately or in different senses by different authors. In a report published in 1959,(1) a WHO Expert Committee on Health Statistics adopted definitions for the two terms. These are reproduced in abridged form below, together with explanatory notes. It is hoped that their further publication will encourage their general adoption, thus ensuring the comparability of data reported by different authors.
D004813:Epidemiology; D009626:Terminology as Topic