In epidemic, 1st step is?
The steps in epidemic investigation are :

Verification of diagnosis
Confirmation of the existence of epidemic
Defining the population at risk
Obtaining a map of the area
Counting the population
Rapid search for all cases & their characteristics
Medical survey
Epidemiological case sheet
Searching for more cases
Data analysis
Formulation of hypothesis
Evaluation of ecological factors
Further investigation of population at risk
Writing the report
Verification of diagnosis
Isolation
Immunization
Notification