It isn't perfect but they said the following:
"The first recorded fever on board the ship was a febrile passenger on day 8. Isolation protocols were immediately commenced, with all passengers confined to cabins and surgical masks issued to all. Full personal protective equipment was used for any contact with any febrile patients, and N95 masks were worn for any contact with passengers in their cabins. The crew still performed duties, including meal services to the cabin doors three times a day, but rooms were not serviced. Expedition staff helped with crew duties at meal service."
Given that they were completely isolated from the outside world for 28 days and isolation protocols on the ship commenced on day 8, my opinion is that it is fair to assume (based on our knowledge of how the virus typically progresses) that most who tested positive would have developed symptoms by day 28 (after 20 days of isolation protocols) if they were going to develop them. Thoughts?