Morbidity refers to the occurrence or presence of illness.

Any attempt to measure morbidity must be preceded by obtaining morbidity data. Where can one obtain information about a person’s illness? If the person was hospitalized, hospital records are useful. However, if the person was not hospitalized, treatment records from various healthcare providers may be required- this depends upon the location, and varies from country/state to country/state. Information about illness before medical care was sought may be obtained by interviewing either the patient or family members.

In order to make appropriate comparisons and interpretations, the source of data must be considered. For instance, hospital records will not capture the true extent of illness in a given population.

Broadly, disease occurrence can be measured using rates or proportions. While rates indicate how fast a disease is occurring in a population, proportions indicate the fraction of the population that is affected.

This two-article series will briefly discuss

1. Incidence Rate
2. Attack Rate
3. Prevalence

While this article will discuss Incidence Rate and Attack Rate, the next article will discuss Prevalence.