If you didn't know. This film is another American-Remake. That's right. Once again, American underlings of the film-persuasion lacked any real originality or motivation to write anything of their own, so they chose to massacre an existing one. That isn't to directly say this movie is horrible. But the strange thing you may notice if you educate yourself is that the ORIGINAL had a plot, where as this one, sadly, comes out with little to NO plot.
Now if you like the common films that have no regard to your intelligence or sense of accomplishment that one can get from watching a good film. (Like 'One Missed Call' 'The Ring' 'The Eye' etc). Then you will think I have no clue what I am talking about. However, if you're not a dolt, you will agree and wonder why this movie delivered the higher budget film, but removed the plot.
The film is 85% it's original. However it does take some originality in developing the 'infection' earlier on in the plot, however you really don't get any explanation on much anything. (It's like they teased you with it. Although the tease being a very weak attempt at a conclusion).
Honestly, you cannot grasp the entirety of this film without watching Rec. The same can't be said inversely, but both are enjoyable to watch.
In conclusion if you just want a drive-by horror. Go ahead. If you actually want to have something to talk about with your friends, get Rec and this one and watch them back to back with the gang and make it your own discussion.