Uh... None of that sounds good. Not to be alarmist or anything but that many complaining of symptoms at the same time and the CDC is all, "Welp... ajust go on your merry way"?
It would be different if they had told us they had a conclusion. "There was a chemical leak on board " etc. 100 out of a manifest of 500 isn't insignificant in terms of an outbreak, at least not to my thinking though I could be wrong. Still... maybe get a conclusion before letting everyone go. Maybe it's nothing but better safe than sorry.