This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
While investigating an epidemic, search for more cases is continued till what period 
Select and explain. 
A. Twice the incubation period of the disease since occurrence of the last case, B. Thrice the incubation period for the disease since occurrence of the case, C. The longest incubation period for the disease, D. Incubation period period for the disease plus two standard detions
A: Twice the incubation period of the disease since occurrence of the last case
Answer: A: Twice the incubation period of the disease since occurrence of the last case 
Explanation: while investigating an epidemic,search for more number of cases is continued till twice the incubation period since the onset of the disease as well as its progression in course of timeref;parks tectbook,ed22,pg 123