Relationship between incidence and prevalence

An interactive simulation.

In a population of 50 people, everyone gets a cold either once or twice a year.

The average duration of each cold is a week. So the incidence of colds is 75 and the duration (in years) is 7/365.

Prevalence = incidence x duration

Therefore prevalence = 75 x 7/365 = 1.438.

So, at any given point in time there will be 1.438 people with colds out of a population of 50.

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Drag the pointer along the timeline and see how the values change. For a pop-up explanation of how each value is derived, move the cursor over the .

Re-starting the simulation generates another set of 75 colds of random (3 to 10 days) duration starting at random times throughout the year.