Introduction to Epidemiology 6th Edition by Ray M Merrill

Exercise 8

Calculate the secondary attack rates for Table 1.

Table 1 Shigellosis Secondary Attack Rates

General Secondary Attack Rates
Questionnaires Returned by	Total Number	Number Returned	Attack Rate %
Families of students	245	169	—
Household contacts	698	97	—
Asymptomatic students	37	5	—

Step 1 of 2

Attack rate can be defined as the rate of number of diseased cases to the number of individual that are followed or at risk.