Prevalence

In epidemiology, the prevalence of a diseasein a statistical populationis defined as the ratioof the number of cases of a disease present in a statistical population at a specified time and the number of individuals in the population at that specified time. For example, the prevalence of obesity among American adults in 2001was estimated by the U. S. Centers for Disease Control (CDC) at approximately 20.9%. In plain English, "prevalence" simply means "proportion" (typically expressed as a percentage).

Prevalence is useful because it is a measure of the commonality of disease. It helps physicianswith the probability of certain diagnosesand is routinely used by epidemiologists, health careproviders, government agencies, and insurancecompanies. Prevalence is not to be confused with incidence, which provides a measure of occurrences of a disease in a specified time interval. Prevalence involves all affected individuals, regardless of the date of contraction. To illustrate, a disease with a long duration that was spread widely in a community in 2002will have a high prevalence in 2003(assuming it has a long duration) but it might have a low incidence rate in 2003. Conversely, a disease that is easily transmitted but has a short duration may have a low prevalence and a high incidence. Prevalence is a useful parameter when talking about long lasting infections, such as HIV, but incidence is more useful when talking about infections of short duration, such as chickenpox.

Lifetime prevalence (LTP) is ratio of the number of individuals in a statistical population that at some point in their life experiences a "case" (e.g., a disorder) and the total number of individuals.

See also

• Incidence
• Rare diseasede:Prävalenz

es:prevalencia fr:Prévalence it:Prevalenza nl:Prevalentie

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It uses material from the http://en.wikipedia.org/wiki/Prevalence Wikipedia article Prevalence.