-Mortalität and mortality refer to the number of deaths per unit of the general population.
-Letalität is the number of deaths per unit of cases of an illness etc. In English the common expression would be fatality rate, or case fatality rate.
-Confusingly there is a German Fatalität which refers to the number of deaths compared to the number of new cases. (cf. Aerzteblatt below), though some sources use it for Letalität.
If out of 1000 people 10 have an operation and 2 of them die
the mortality or death rate would be 2/1000 = 0.2%,
the case fatality rate would be 2/10=20%.
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Many definitions on:
http://medical-dictionary.thefreedictionary.c...Letalität als Quotient aus Mortalität und Inzidenz - mortality / incidence.
Fatalität Verhältnis von Sterbe- und Zugangsraten - death rate / new incidence rate
cf.
http://www.aerzteblatt.de/archiv/31723Mortality = deaths (for a given illness)/unit of population (100,000 sick and well)
Fatality = deaths per 100 cases of a given disease.
cf.
http://pediatrics.aappublications.org/content...
