Plot hole: When the survivors first make an attempt to break out towards the station they kill numerous assailants at close quarters and yet only one of them (Uno) is infected. There must be dozens of the parasites floating around, enough to infect them all.
Continuity mistake: After Melanie's "plan A" failed since the train is not at the station the group fights its way back to the prison. During that fight they kill quite a lot of the possessed miners. But in one of the following scene when those freaks assemble in the streets and walk to the prison there are only four or five bodies lying around.
Melanie Ballard: Well, introduce us to your friends.
Desolation Williams: These are my compadres, Uno, Dos and Tres.
Melanie Ballard: Uno must be the nice one.
Uno: You got that right, butchy. I'm not as nice as Desolation. And I'll cut your fucking titties off.