Class of the Dead

A vaccine set up to help the world mutated to form an unstable deadly disease that turned the living into death marchers. The disease wiped out more than 90% of the world's people, leaving few behind to attempt to survive. As the death marchers spread the disease further with their bites and killing more with their appetite for living flesh, those who are left are put at even worse odds. A city of over one million was destroyed by a herd of death marchers, leaving only 45 high school students and teachers behind. The group, led by seventeen year old Morgan Tendrom, must battle the new world of the dead. Some live, some die, but all are changed when faced against the force of the dead.

Photo in cover not mine. Found it on Internet.