Mortality rates measure the frequency of occurrence of death in a defined population during a specified interval.

There are several specific kinds of mortality rates, but we will focus only on the ones that are used most often in infectious disease epidemiology.

To calculate a simple mortality rate, we need to know the number of deaths in a given population during a specified time period, and the size of the
population in which the deaths occurred. The basic formula is:

The most commonly used values for 10ⁿ are 1,000 and 100,000.

Crude Mortality Rate

The crude mortality rate is the mortality rate from all causes of death for a population during a specified time period.

The denominator is the population at the mid-point of the time period.

For example, the crude mortality rate for Missouri in 2003 was 896 deaths per 100,000 people.