Zombies and the chances of an outbreak.

Zombies are a very odd race of creatures. They are sometimes pictured as nothing but the reanimted corpse of a deceased being. Sometimes, as a Body that has been used as a vessel for an evil spirit released from Hell feeling the need to cause chaos. A being who has been cursed by a voodoo curse, or any other kind of curse for that matter.And sometimes they are but a being that has been infected with a horrid virus. The possibilities are seemingly endless and yet, this is a thing that most peiople merely laugh at. The actual chances of a zombie epidemic of some sort is incredibly high in my own opinion. How it would be started I do not know, but it is still a possibility. I want to know exactly how most people believe zombies will come to exist and which cause seems the most reasonible in youer opinion.