The sickness

A 17 year old girl named Airyan is living in a world of chaos, infected by the horrible and mysterious "Sickness" that had plagued the Earth. Her and her best friend and training partner, Leo are Marked children or, the select few of the new generation who are immune to the sickness. They are trying to survive in their broken town, protect Leo's little sister, fight the Sickness, and possibly find Leo's parents who have been long at war. Soon they meet a dog they name Cheerio who changes their lives forever.