Creating Epidemiology, the difference between Prevalence and Incidence

Meaning of Epidemiology:

Epidemiology is the study of the distribution and determinants of health related states or events. And the application of this study to the control of diseases and other health problems.[1]

It studies the health of population groups within societies or countries. This information helps plan health programs to know how one country’s health compares with another, and many other things that are useful for all who work in a health setting.[2]

Difference between Prevalence and Incidence:

Two of the most commonly used terms in epidemiology are prevalence and incidence, and they are often mixed up or used incorrectly.[2]

What is incidence?

It is the number of instances of illness commencing or of persons becoming ill (injured or dying or hurting) during a given period in a specified population. In other word, incidence usually means something that is measured within a set number of people and in a time period.

Example of incidence:

Auckland in New Zealand, often has epidemics of meningococcal disease, with annual incidences of up to 16.9/ 100,000 people.[2]

What is prevalence?

It gives a figure for a factor at a single point in time (samples of a study, rate of specific case in a hospital etc.) i.e. prevalence can tell us only what is happening at a certain point.

Example of prevalence:

A recent Scottish study showed that the prevalence of obesity in a group of children aged from 3 to 4 years was 12.8% at the time.[2]


  1. epidemiology, health topics, (accessed 28 August 2017)
  2. 2.0 2.1 2.2 2.3 Linda Shields and Alison Twycross, the difference between incidence and prevalence, vol 15 no 7 September 2003.