I just have to say....every time we go on a cruise at least one person in our family comes down with a terrible cold. Is it anyone's fault, of course not. Between being on the plane and being on the ship you get exposed to all sorts of things. You can't help it. Kids are exposed everyday to all kinds of illnesses.
To the OP....pack your bags, come to the US and enjoy your vacation!!!!
To the Worry Wort who had to stick her nose were it doesn't belong and contact
DCL - You need to get a life!!!!! If you are that worried....stay home. Do you really think the OP's kid is going to be the ONLY kid on board that was exposed to CP or some other ailment. Absolutely Not!!!!