This is an excellent article. As it pointed out, cruise ships are required to report to the CDC when 2% of people abord (crew or guests) have any form of illness. In contrast, our local school system does not have to report to anyone until 10% of personnel are out sick. That helps to explain why so many more reports of "infected" ships occur.
BTW, on their most recent inspections, the Magic scored a 94, the Wonder scored a 98. The CDC rates anything above 86 as "acceptable," and only 3 ships received a perfect 100 in their most recent inspection.