You make instruments out of human bones
You start robbing graves to make your series of ribcage xylophones and femur flutes. You are working with these new instruments all the time. That's how you get the zombie rot: a bone shard penetrates you wrist, and the wound just keeps getting nastier. A horrid smelling black pus must be drained from it more and more often. You feel cold and tired and you throw up a lot. You are finally too weak to rise up from bed. That is too weak to rise up until you are dead. You then start a massive zombie outbreak in our city.
