This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
[{'content': 'The severity of disease is assessed by \nSelect and explain. \nA. Case fatality rate, B. Standardized mortality rate, C. Incidence rate, D. Prevalence rate', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 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.\nTotal no. of deaths due to particular disease x 100. Case Fatality rate = Total no. of cases due to same disease.\nCase fatality rate is typically used in acute infectious diseases e.g. (food poisoning, cholera, measles)\nIts usefulness for chronic disease is limited because the period from onset to death is long & variable.\nThe case fatality rate for the same disease may vary in different epidemics because of changes in agent, host & environment factors.', 'role': 'assistant'}]