Planet Urth (Book 1) a post apocalyptic novel by Jennifer and Christopher Martucci

http://www.amazon.com/Planet-Urth-Book-Series-ebook/dp/B00FKKWQXY

Fast forward to the post-apocalyptic future, over 200 years from the present. Following a horrible war, the few inhabitants left on Earth are plagued by disease and imminent death. Chemical warfare has caused mutations in the human species, producing a new terrifying group of mutants called Urthmen. These creatures rule the ruins of North America. There are a few humans left, one of which is a brave young woman named Avery. As the sole guardian still living, she must fight to protect her younger sister. When their city is overrun by Urthmen, they’re forced to retreat deep into the forest- but are they truly alone?