In The Flesh(Teeth)

Rule number one for surviving a Breather-filled world:

Never travel alone.

They came from the night, beginning with mutilations and disappearances. When humans became comfortable with the safety that light seemed to offer, they attacked in the day. It only took a short time for the Breathers to take over.

What's left are stragglers struggling to survive, humans enslaved in blood farms, and those who serve as blood slaves.