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Case fatality rate

Last revised by Dr Ayla Al Kabbani on 24 Apr 2020

The epidemiological term, the case fatality rate (CFR) (also known as case fatality ratio, fatality rate or lethality rate) is a proportion from the number of individuals who having been diagnosed with a disease, that shows how many die from that disease in a given time period. Following from this, the numerator is the number who have died from the disease in a specified time period, and the denominator is the overall number who have been diagnosed with that disease.

NB: Case fatality rates are inherently susceptible to certain biases. In diseases where there are asymptomatic or mild cases, there may a significant under-diagnosis of the disease relative to its true numbers in the population. In such cases, a case fatality rate would overestimate how lethal a disease is. In diseases where there can be a long period before death, if the time period given is too short, the case fatality rate may underestimate how lethal the disease is.

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