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
The first step in the investigation of an epidemic is which of the following? 
Select and explain. 
A. Verification of diagnosis, B. Confirmation of the epidemic, C. Defining the population at risk, D. Formulation of hypothesis
A: Verification of diagnosis
Answer: A: Verification of diagnosis 
Explanation: Verification of diagnosis is always the first step and writing repo is the last step of an epidemic investigation. Ref: Park's textbook of Preventive and Social Medicine, 21stedition, page-119