Some research shows that this virus has always been around. However it hasn't been until the post 9/11 worries over bioterrorism that has truely about it out to the public eye.
It is actually somewhat rare for someone not to get sick (not talking about sea sick) on a large cruise ship. It's when it becomes multiple people people in the triple digits that things become worry some.
There is no real sure way to prevent the illness. There are lots of precautions but no way to really stop it from occuring.
Mandy, it should be safe, if people practice common sense while on the ship.
One think you might check, as Jerry Nuovo and I noticed it for the QE2 and the Queen Mary 2: at places where people congregate, and equipment usage is shared, there should be hand sanitizer dispensers handy; use those early, and often.
That will be noticed in self-serve food areas, computer use rooms (including the library) and the gymnasium.