<prompt> While investigating an epidemic, search for more cases is continued till what periodTwice the incubation period of the disease since occurrence of the last caseThrice the incubation period for the disease since occurrence of the caseThe longest incubation period for the diseaseIncubation period period for the disease plus two standard detions  <response>: 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 