Deathwatch. The Faded Earth, #1

Humanity was on the cusp of greatness when the Fade began to spread. Cities fell during the decades known as the Collapse. The spread of the disease turning human beings into bloodthirsty monsters could not be stopped. It could not even be slowed. Weapons of mass destruction burned half the world down to the bedrock. Yet some survived. Using technology meant to take men to the stars and find a new home there, the immune took refuge.
They were the seeds of a future not yet written. A hope for a better world. Armed and armored, they set about rebuilding from the ashes. A century later, North America is all but unrecognizable. Survival has ceased to be an idea--it is almost a religion. The needs of the many outweigh all else. This is a lesson Rebecca Park will learn in the harshest way imaginable. When her family is torn away from her, she will face a choice unlike any in her short life.
Wallow in grief and fade away like so many before her have, or choose to make herself into something more. Drawn into a fight she could never have imagined, Beck will face the monstrous Pales who have overrun the badlands and the darkest parts of the people around her. It is a life few ask for. A life fewer still make it through to old age. That is how it almost always ends for those who choose to be the shield for the rest of humankind.