Difference between revisions of "Measures of disease frequency"
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==Prevalence== | ==Prevalence== | ||
| + | The prevalence of a disease is the proportion of animals in the population of interest which are 'diseased' at any specific point in time. This may be a single point (in which case, the measure is the '''point prevalence'''), or may be over a period (in which case the '''period prevalence''' is given). However, it is important to realise that this measure will therefore include both old and new cases of disease. The prevalence can be viewed at an individual animal level as the 'probability that an animal selected at random from the population will be diseased'. | ||
==Incidence== | ==Incidence== | ||
Revision as of 13:13, 4 May 2011
A very common aim of epidemiological investigation is to estimate the levels of disease in a population. This is of particular importance in the case of surveillance and disease monitoring systems, and is commonly the central aim of many descriptive studies. There are two main measures of disease frequency - the prevalence and the incidence of disease, which each measure different aspects of disease. The time to event is another measure commonly used, and is closely related to the incidence.
Prevalence
The prevalence of a disease is the proportion of animals in the population of interest which are 'diseased' at any specific point in time. This may be a single point (in which case, the measure is the point prevalence), or may be over a period (in which case the period prevalence is given). However, it is important to realise that this measure will therefore include both old and new cases of disease. The prevalence can be viewed at an individual animal level as the 'probability that an animal selected at random from the population will be diseased'.