Embarassingly bad
I can't believe that Eli Roth was allowed anywhere near a movie production again after this, let alone considered some sort of horror mastermind.
The plot and dialog could've been written by a 12-year-old, the movie adds nothing new to the "teens on vacation" trope (which I enjoy, BTW, when done well), and there was none of the terror that you feel when watching good plague movies.
Really, I don't get it, especially the idea that this is supposed to be some cult classic.