the total number of persons who have an attribute or disease at a particular point in time divided by the size of the population at risk of having the attribute or disease at this point in time (or midway through the period), usually expressed as the number of cases per 100,000 persons.
Notes:
This is the operational definition. It is commonly used even by international organizations in lieu of a more technically correct definition which is often not supported by readily-available data. Also, prevalence ratio or what is commonly known as prevalence rate. When prevalence is used to mean prevalence proportion at a point in time, then calling it a prevalence rate is technically wrong.