Dog Blood by David Moody

The world has suffered a catastrophe of unknown cause, dividing humankind into two: the Haters and the Unchanged. Each group believes the other to be the enemy; each group is fighting for survival. Only by working together can the enemy - whoever that enemy is - be defeated. There are no other choices. Danny McCoyne has managed to break free, and after days of indiscriminate fighting and killing, he is determined to make his way home, to recalim the only thing of any value to him in this strange new world: his daughter Ellis. Unlike his wife and son, Ellis is like him, and he knows, in his heart of hearts, that she is not dead. His dearest wish is for Ellis to be fighting for the world at his side - but Danny soon discovers his daughter is worth far more than just another fighting body. Others like him have discovered that children are absolutely vital to the cause. They are strong, small, fast, and they have no inhibitions. They are pure Haters...

This book is part of the "Hater" series.
Here are some other books from this series: