Epidemic mortality is usually given as a percentage. It is defined as that percentage of the population which dies during an epidemic.
The equation for epidemic mortality is:
lethality X morbidity = epidemic mortality
In cases where the exact nature of a disease is in debate, as for instance in the more abstruse debates among medical historians about the nature of the organism (or organisms) that caused the Black Death, the equation above may be used to double-check the results of demographic studies of an epidemic.