This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Concept of health and disease, Subject name: Social & Preventive Medicine
Purpose of sentinel surveillance is 
Select and explain. 
A. To know total number of cases, B. Health planning, C. Prevention of disease, D. To know natural history of disease
A: To know total number of cases
Answer: A: To know total number of cases 
Explanation: A method for identifying the missing cases and there by supplementing the notified cases is required. This is known as sentinel surveillance. The sentinel data is extrapolated to entire population to estimate the disease prevalence in entire population