Board Thread:Questions and Answers/@comment-104.172.189.120-20150505044206/@comment-62.183.154.102-20160222150734

^^ No, ghouls aren't the result of a virus or some supernatural thing. The only way for a human to become a ghoul is a kakuhou transplant.

Also, the ghouls of TG are not the same thing as the mythological creatures. They're just named after them.