prevalence disease prevalence is a ratio formed by the number of subjects diagnosed with a disease divided by the total population size. A proportion in which the numerator represents all events of interest (for example, both new and preexisting cases of a disease) in the population, which is represented by the denominator. Brian S. Alper, Muhammad Afzal, Joanne Dehnbostel, Janice Tufte, Kenneth Wilkins, Harold Lehmann Philippe Rocca-Serra adapted from: https://www.health.ny.gov/diseases/chronic/basicstat.htm proportion ready for release