Out of 10 relatives exposed to a primary case, of measles, 6 developed measles. Secondary attack rate of measles-

Ans. is 'b' i.e., 6/10 Secondary attack rate (SAR)o SAR is defined as "the number ofexposed persons developing the disease within the range of incubation period, following exposure to primary caseSAR=No of exposed persons developing disease withinthe range of the incubation period-----------------------Total number of exposed/susceptible contactx 100 SAR =610x 100