PHRD554 Public Health Practice Test

Prevalence measures how much disease burden exists in a population at a specific moment by counting how many people have the condition and expressing that as a share of the population. In other words, it’s the number of existing cases per population at that time, typically shown as a percentage or per 1,000 people. This distinguishes it from incidence, which counts new cases over a defined period. If you only use the total number of cases without relating it to how many people are in the population, you don’t get a true prevalence measure. For example, in a city of 20,000, if 150 people have the disease on a given day, the point prevalence is 150/20,000 = 0.75%.