Lethality rate (case fatality rate)
The lethality rate is a statistical tool used in epidemiology to assess the severity of a disease.
In particular, the lethality rate of a pathology expresses the number of deaths (for a given disease) in relation to the number of patients (of this disease).
The formula for calculating the lethality rate is: L = (N / P), where:
- L = lethality rate expressed as a percentage
- N = total number of deaths for a given disease
- P = total population of subjects affected by this disease
For example, if a disease affects 1, 000 people causing 100 deaths, the fatality rate is 10%.
Mortality rate
The lethality rate should not be confused with the mortality rate. The latter, in fact, expresses the relationship between the number of deaths in a population over a given period of time and the average quantity of this population in the same period. It can therefore be expressed by the formula: annual number of deaths / number of people belonging to the population in that year.
For example, if every year 200, 000 people die from cardiovascular disease in Italy, considering that the number of inhabitants in Italy is 60, 000, 000, the mortality rate from cardiovascular diseases is about 0.333%.
