Exactly. Truthfully it doesn’t matter if THEY contracted it at Disney or not. If they contracted it before getting there it only means they were contagious the whole time they were there potentially exposing anyone else they had any contact with during their stay and during their travel to and from. So brushing it off as “they probably already had it” is silly because while it would mean THEY didn’t catch it there, it doesn’t take away the fact that them having it at all exposed other guests. Hopefully they followed the rules and behaved responsibly during their stay and did not pass it on to anyone but these are the kinds of scenarios people need to be thinking about before they move forward with their trips.