Editing Prevalence (section)

==Examples and utility==
In science, ''prevalence'' describes a [[ratio|proportion]] (typically expressed as a [[percentage]]). For example, the prevalence of obesity among American adults in 2001 was estimated by the U. S. [[Centers for Disease Control and Prevention|Centers for Disease Control (CDC)]] at approximately 20.9%.<ref>{{cite web |url=https://www.cdc.gov/nccdphp/dnpa/obesity/trend/prev_reg.htm |archive-url=https://web.archive.org/web/20060624145234/http://www.cdc.gov/nccdphp/dnpa/obesity/trend/prev_reg.htm |access-date=2017-09-10 |archive-date=2006-06-24 |title=Overweight and Obesity: Obesity Trends &#124; DNPA &#124; CDC }}</ref>

Prevalence is a term that means being widespread and it is distinct from [[incidence (epidemiology)|incidence]]. Prevalence is a measurement of ''all'' individuals affected by the disease at a particular time, whereas incidence is a measurement of the number of ''new'' individuals who contract a disease during a particular period of time. Prevalence is a useful parameter when talking about long-lasting diseases, such as [[HIV]], but incidence is more useful when talking about diseases of short duration, such as [[chickenpox]]. {{Citation needed|date=October 2018}}