Case fatality rate
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.