The Different Reasons Most Used

Agent 807
A new slayer is to be called. You are to become a new watcher. If you can pass the finals.
What are the three most common reasons that vampires exist? And Do try to be realistic.

1. Supernatural. A race of vampires that are not really human to begin with like from space or a demon recalled.
2. Lab sickness. Usually while in the search for a cure for something else, a mutation of the human DNA creates a virus.
3. Natural evolution. An offshoot of humans who have developed along with us.

Excellent. Now, Agent 807, what are some field cases of the three most used vampires?

1. Virus (Lab Sickness) such as Red Blooded American Girl, Rein of Blood, Against the Dark and Perfect Creature
2. Supernatural (demons or aliens) such as Vamperella, Lifeforce, Shock'em Dead, Stay Alive, and the Stuff
3. Natural Evolution. such as Bram Stoker's Dracula, Nightbreed, and Underworld

You have just passed your first level exams.