In: Statistics and Probability
In the Fall semester, 112 students attended a 5-day field trip to Washington DC. During the trip, 43 of the students became ill with norovirus, a highly contagious gastrointestinal illness that is shed in the feces of infected persons. All of the students who attended the field trip live in the same dormitory, which houses a total of 438 residents. In the week following the return of the travelers, another 168 dormitory residents became ill with norovirus. Over the course of the primary and secondary outbreaks, 2 students died as a result of complications from norovirus infection.
Question: What is the Secondary Attack Rate (SAR) of norovirus in this outbreak?
* I am having trouble understanding if you should subtract the pre existing cases from the total exposed denominator I just need some clarification thank you