The turning does not work by a single bite. Have you seen Interview with the vampire? Its the best vampire film I've ever seen, and thats how I portray the turning to work... the vampire drains the human to almost death, and then gives him/her the choice to drink the vampire's blood (and become a vampire) or die.
And I don't believe in any of this, but it makes interesting stories. Satan in my imagination is God's brother. Not an evil one, mind you, but not purely good. God crated Adam and Eve in the garden of Eden as an experiment to see if humans will work as a race. The apple tree of sin was placed there to test their will power against giving into temptation. Gold told Adam and Eve that the sin tree would cause the world to become full of sin. he just made this up to scare them both and to make the experiment more tense. The experiment was really to see if Humans would sacrifice others for their own pleasure (eating a delicious paple would cause sin to cover the world). Eve picked the apples off the tree, but shared them with Adam. Both gave into temptation.
God was not pleased with the result and decided to kill Adamn and Eve and try something else. Satan (Lucifer) did not approve of this... killing huamns for eating apples... he thought that they just didn't understand what sin would cause, it wasn't even real. God ignored his brother and killed Adam and Eve. Satan was angry at this and protested against God. Fuming with anger, God killed his own brother, casting him into a flaming pit and creating "Hell", the prison to trap his spirit. There, Satan was now a fallen angel (Him being a high angel before with not as much authority as God had). Almost everybody in heaven was in favor of God's decision. Those who wasn't cast themselves into hell to join Satan. Enraged with anger, they formed together and overtook Hell and made it their own domain. God lost any interest he could spare for Satan, and was too busy on his new project... the Apes.
He decided to create ape men/woman that was slowly evolve into humans, to see if the result would be more pleasing for him. Meanwhile, Satan believing that God was full of sin started up his own army against God. However, nothing was heard from them until apes were almost fully evolved into men and women, and were learning about god. Satan was angered that they were taught that God is good and satan is evil and all that razamatazz. It was Satan who created vampires. They were sent up to convert men and women or kill those who refuse. This would expand Satan's army. These actions were just as evil as those done by God. God originally created his own vampires to kill off Satan's vampires and to protect the humans. But as a thousand years went past (after the birth of jesus), God wasn't happy once again with the way humans were turning out. With them disbelieving in him and some being totally evil, he decided to kill them off by sending his vampires down once again. Now it is Satan's vampires who protect humaity, yet they still try to turn more human beings into vampires.
Satan's hatred for his brother had driven him quite insane and goes to any lengths to hurt him or convince others to hate him. God keeps it more cool, letting his angels, vampires and other species do the work for him.
And this is the brief version. this is actually what the story of one of my games is based on 
What's your favourite supernatural creature-(s)?
the supernatural creature in Japan...
???
super natural
