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': 'False regarding a propagated epidemic is - \nSelect and explain. \nA. No secondary waves, B. Spread depends on herd immunity, C. Person to person transmission occurs, D. Slow rise', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Propagated epidemics \n\nPropagated epidemic is most often of infectious origin. -\nIt results from person to person transmission.\nSource of disease agent is not common to all cases. Every new case becomes the source for others.\nThe epidemic usually shows a gradual rise and tails off over a much longer period of time.\nThe speed of spread depends upon herd immunity, opportunities for contact and secondary attack rate.\nPropagated epidemics are more likely to occur where large number of susceptible are aggregated, or where there is a regular supply of new susceptible individuals (e.g. birth, immigrants) lowering herd immunity.\nTransmission continues until the number of susceptible is depleted or susceptible individuals are no longer exposed to infected persons or intermediary vectors.\nEpidemic continues over more than one incubation period.\nSecondary waves are seen.\nExamples - epidemic of polio and Hepatitis A.\n\nAlso know\n\nA typical type of epidemic is epidemic of cholera.\nIt starts as common source-epidemic → most of the initial cases acquire the disease from a common source (e.g. a well with contaminated water).\nThen it continues as a propagated epidemic → these cases become the source for the other persons in their close vicinity.\nSo it has a sharp peak but tails of gradually over a longer period of time.', 'role': 'assistant'}]