Meteors carrying microscopic parasites shower the Earth, unleashing a deadly alien virus that essentially creates billions of zombies worldwide. These zombies are constantly pumped with adrenaline so they are faster, stronger and "Mitt Romney-gunning-for-the-presidency" level rabid.
The world's governments unite to enact The Pain Killers Program, wherein recently infected test subjects from around the world are inoculated with an experimental vaccine in hopes of finding a cure-- IT FAILED.
The chemical reaction between the serum and the alien parasites proved too unstable, hundreds died but the few who survived found themselves genetically changed. They developed superpowers. Now they have a fighting chance at survival. It's zombies versus superheroes
