Case fatality' rate is -

Ans. is 'a' i.e.. Severity of disease Case fatality rate (ratio)o CFR represents the killing power (severity) of a disease.o CFR is typically used in acute infectious disease e.g. food poisoning, cholera, measles.o Its usefulness in chronic disease is limited, because the period from onset to death is long and variable,o CFR is closely related to virulence of agento Limitation of CFR is that time period is not specified.o The case fatality rate for the same disease may vary in different epidemics because of changes in host, agent and environment factors.o Case fatality rate is the complement of survival rate.CFR = 1 - survival rateo CRF will be more if survival rate is less - more patients are dying due to disease (TCFR) or in other words less patients are surviving (-1 survival rate).