Prevalence is a measure of frequency of an illness, disease, or health conditions. Unlike incidence, which reflects new occurrences or changes in health states, prevalence is concerned with already existing health conditions, regardless of whether that health condition is of recent onset or is long-standing. Thus, prevalence of a particular condition refers to the proportion of the population which has that condition at a specified time. It is usually presented as x cases per 1,000 (or 10,000 or 100,000) people in the population. There are two types of prevalence: point prevalence (the type of prevalence most commonly reported) and period prevalence. Consider the example of the common cold. The “point prevalence” of the common cold in New York City means the proportion of people in New York City with a cold at a given point in time, i.e., the number of New York City residents with a cold on a specific day divided by the total...
References and Readings
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