The case fatality rate (CFR) is a measure of the severity of a disease, calculated by dividing the number of deaths due to the disease by the total number of diagnosed cases. It directly indicates the proportion of fatalities among individuals already identified with the condition, reflecting the deadliness of the disease. Unlike incidence or prevalence, CFR does not measure new or existing cases but focuses exclusively on outcomes of diagnosed patients. This measure is crucial for assessing the effectiveness of treatments and healthcare responses during outbreaks.

Reference: Principles of Epidemiology, Rose E. Ashcroft, 3rd Edition.