The bottom line (***SPOILERS***)
"Carriers" is an excellent -- albeit decidedly melancholic -- depiction of a post-apocalyptic world where conventional law & order are nonexistent. The film successfully stimulates moral reflection and is engrossing from beginning to end. Although it looses points for being too downbeat...
...especially the climax. C'mon, the dude makes it to the remote beach and he has a hot lass at his side; they could be the new Adam & Eve, but all he does is whine like it's the end of the world or something.