The severity of disease is assessed by

Case Fatality rate represents the killing power of the disease, it is closely related to virulence. It is simply a ratio* of death to cases. Total no. of deaths due to particular disease x 100. Case Fatality rate = Total no. of cases due to same disease. Case fatality rate is typically used in acute infectious diseases e.g. (food poisoning, cholera, measles) Its usefulness for chronic disease is limited because the period from onset to death is long & variable. The case fatality rate for the same disease may vary in different epidemics because of changes in agent, host & environment factors.