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': 'Spot map is used for- \nSelect and explain. \nA. Local distribution of disease, B. Rural-urban variation, C. National variation, D. None', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' i.e., Local distribution of disease o Inner and outer city variations in disease frequency are well known. o These variations are best studied with the aid of "spot maps" or "shaded maps". o These maps show at a glance areas of high and low frequency, the boundaries and distribution. o For example, if the map shows "clustering" of cases, it may suggest a common source of infection or a common risk factor shared by all the cases. o The classical example of use of spot maps was by John snow for cholera epidemic in 1854.', 'role': 'assistant'}]