1. Earlier this year, investigators studied a cluster of COVID-19
cases among passengers on a 10-hour commercial flight. Flight VN54 departed London at 11:10 am local time on March 1, 2020, and arrived in Hanoi at 5:20 am local time on March 2, for a nonstop flight lasting about 10 hours. A total of 217 people – 16 crew members and 201 passengers – were on board. (You can – but you do not have to – find a detailed description of the investigation here.) An initial investigation led the investigators to hypothesize that the cluster of Covid-19 cases originated from one symptomatic passenger (called the ‘index’ case). They subsequently launched an extensive epidemiologic investigation that involved testing and isolation/quarantine of all traceable passengers and crew members. They identified an additional 15 COVID-19 cases – 14 passengers and 1 crew member – resulting in a total of 16 confirmed flight-associated cases (including the index case).
Which measure of disease occurrence is the most appropriate to calculate for this investigation? [ ½ ]