USA Today: "Cruise ship heads home after illness outbreak"
. . . Dr. Andrew Coggins, who teaches courses on travel and tourism management at Pace University, says a passenger likely brought the virus onboard after his or her symptoms subsided. "Last-minute cancellations usually result in forfeiting the cruise fare so if someone doesn't have travel insurance they are going to try to make the cruise as long as they can get from toilet to toilet," he said.
"RCI is taking the right action," Coggins said. "By returning early, they will get everyone off the ship and can do a thorough top-to-bottom disinfection. It will be very expensive in terms of lost revenue, refunds, and bad publicity, but they will protect the next sailing."