I was reading where it was not only the Magic, but a Holland America cruise ship. Disney is super washing down the whole ship away from port so it won't transmit or pick up any more viruses. Since it can be passed from one contaminated person to another, it could have been picked up in a port of call.
Everyone I know who has been on a cruise never experienced anything like this and I hope it doesn't happen to often, especially for Disney cruises.