DHSS Home State Home Ask Us Disclaimer   
  Module IV
dot Home
dot Objectives
dot Using Statistical Measures
dot Frequency Distributions
 - Ratios
 - Proportions
 - Rates
dot  - Incidence Rates
 - Rate Ratios
 - Prevalence Rates
dot  - Crude Rate
 - Cause-Specific Rate
 - Other Specific Rates
dot  - Relative Risk
 - Odds Ratio
dot Outbreak Exercises
dot Quiz
dot Outline

Statistical Measures

Group of People

Morbidity Frequency Measures

Prevalence Rates

Prevalence (Prevalence Rates)

Prevalence is the proportion of people in a population who have a particular disease at a specified point in time, or over a specified period of time.

  • The numerator includes not only new cases, but also old cases (people who remained ill during the specified point or period in time). A case is counted in prevalence until death or recovery occurs.
  • This makes prevalence different from incidence, which includes only new cases in the numerator.
  • Prevalence is most useful for measuring the burden of chronic diseases such as tuberculosis, malaria and HIV in a population. The formula for calculating prevalence is: