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
Spot map is used for- 
Select and explain. 
A. Local distribution of disease, B. Rural-urban variation, C. National variation, D. None
A: Local distribution of disease
Answer: A: Local distribution of disease 
Explanation: 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.