why do i get the feeling that MC is infected, i mean think about it, MC gets stronger as he damages and kill zombies and humans, and zombies get stronger as they eat humans and zombies, the few times we have seen a zombie mutate it was just after eating someone, and we also seen that when MC evolved it had a lag between when he got points and when the evolve took place, so it seems they work the same way if we assume said zombie was the one who killed that human.