How is the case fatality rate calculated?

• A. CFR = incidence divided by prevalence.
• B. CFR = (number of deaths from a disease / number of diagnosed cases of the disease) over a specified period.
• C. CFR = total population divided by number of deaths.
• D. CFR = number of diagnosed cases divided by number of recoveries.

Answer: (B)

Case fatality rate measures the proportion of diagnosed cases that die within a defined period. It is calculated by dividing the number of deaths from the disease by the number of diagnosed cases of the disease in that period, usually expressed as a percentage. This directly captures the fatality risk among people who have been identified as cases during the specified time frame. The other formulations mix different epidemiological counts: incidence divided by prevalence isn’t a measure of fatality among cases, a crude population-to-deaths ratio isn’t CFR, and using diagnosed cases over recoveries excludes the death outcome entirely. So, the method that uses deaths divided by diagnosed cases over the same period is the correct approach.