Patient Zero

This is the story of a man. His name is John Addison.
His story is not a happy one, so if you're looking to be uplifted I suggest you search elsewhere.
But his life was not always full of death and despair. He used to have a peaceful life. Not the best, but certainly not the worst.
All of this changed because of one thing.
Him.
He became the world's end, he caused it!
He is the patient zero.