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.
1) what is the attack rate (ar) of norovirus in this outbreak? interpret the result.
2) what is the secondary attack rate (sar) of norovirus in this outbreak? interpret the result.
3) what is the case-fatality rate (cfr) of norovirus in this outbreak? interpret the result.