In a school within an unimmunized coho of 100 children, 1 child developed measles on January 1st. Following this, 35 children developed measles of which 3 cases occured on January 3rd and the remaining 2-3 weeks later. What is the SAR ?

Ans. is 'b' i.e., 33.3% Primary case = 1 o Children developed disease after first case = 35 o Out of these, 3 occured within 2 days of the first case ---> These cases are not due to exposure to first case because minimum IP of measles is 10 days after fever and 14 days after rash. So, minimum 10 days are required to develop clinical manifestations after exposure, i.e., incubation period.