User blog comment:Tommy,Klaus&Kol2012+/How to Kill a Levithan/@comment-1509826-20120225200521/@comment-3481504-20120225204640

Well, the Leviathans were the first beings to inhabit the Earth, and they can't get sick, and there was no sickness thus nothing to get sick. Look, canon doesn't always have to be word-for-word.