The case-fatality rate is the proportion of persons with a particular condition (cases) who die from that condition. It is a measure of the severity of the condition. The formula is:
The case-fatality rate is a proportion, so the numerator is restricted to deaths among people included in the denominator. The time periods for the numerator and the denominator do not need to be the same; the denominator could be cases of HIV/AIDS diagnosed during the calendar year 1990, and the numerator, deaths among those diagnosed with HIV in 1990, could be from 1990 to the present.
A mortality rate is a measure of the frequency of occurrence of death in a defined population during a specified interval. Morbidity and mortality measures are often the same mathematically; it’s just a matter of what you choose to measure, illness or death.
How is CFR Determined?
CFR is presented as a percentage (0%-100%) or a ratio (between 0-1) and measures the number of confirmed deaths among the number of confirmed diagnosed cases of a particular disease at a given time.
Case Fatality Rate (CRF) measures the severity of a particular disease by defining the total number of deaths as a proportion of reported cases of a specific disease at a specific time.
This is different from general mortality rates which are the number of general deaths that occur within a population (normalized to the population) at any given time.