40. Religious Cult
Remember, our definition of a zombie is used from trusted Webster. In this, religious cults make total sense because of the possibility of resembling zombie-like activity. Decades ago, there was a religious cult that had to drink real blood from humans. At least, that was the implication was. They were also said to be cannibalistic.
This means that their cult ate other humans, which obviously had human blood with it. This may not technically be what we look to as a zombie but it fits the definition of the term. Not only because of the connection they have to cannibalize their own but also because a real zombie apocalypse could happen if something like this were to become bigger.