Changes

==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, which can be a problem when attempting to investigate risk factors for a disease of long duration (as many of the diseased animals are likely to have had the disease for some time). 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'. The prevalence of disease is commonly obtained from [[Study design#Descriptive studies#Surveys|surveys]] or cross sectional studies, although in some cases, it can be estimated from a cohort study.

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, which can be a problem when attempting to investigate risk factors for a disease of long duration (as many of the diseased animals are likely to have had the disease for some time). 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'. The prevalence of disease is commonly obtained from [[Study design#Surveys|surveys]] or cross sectional studies, although in some cases, it can be estimated from a cohort study.

==Incidence==

==Incidence==