Epidemiology is the statistical study of the occurrence, distribution, potential causes and control of diseases and disabilities in human populations. The population under investigation could be the entire world, as in the case of a global influenza epidemic, or it could be a relatively small group of people – a single high school, for example, with an unusually high number of adolescents with asthma. Epidemiological data includes:

• counts of illnesses and disability (morbidity data)
• counts of deaths from specific causes (mortality data)
• risk factors for health problems (i.e. factors such as smoking or exposure to toxic waste that increase the likelihood of a disease or disability occurring)
• health promoting factors (e.g. balanced diet, physical activity).

All of these types of epidemiological data are useful for developing your community profile.

Why is it important to document morbidity?

While it is important to identify and prevent health problems that kill people, it is also important to address causes of illness and disability that occur in your community without leading to death. To get a complete view of problems facing you as a health service provider, both mortality and morbidity must be considered. Morbidity is far commoner than mortality. By studying morbidity, it is possible to get a better idea of the pattern of disease and its possible causes as well as identifying incorrect management of cases that result in mortality. In conditions where deaths are uncommon, it is particularly useful to study patterns of morbidity. The causes and avoidable factors of mortality and morbidity are usually the same.