In general, cruise ships carry about half as many crew as passengers. Yet in each case, the number of crew affected was 10% or so of the passengers -- one/fifth of what would be expected!
Could that be because handwashing and other sanitary procedures are constantly hammered at to the crew? Every cruise I have ever been on I have seen passengers bypass the hand sanitizers and men leaving the rest room without washing their hands.
Cruisers -- WASH YOUR HANDS!!!