Sounds like the start of a joke, I know, but I'm not kidding. Vampires and werewolves reproduce by 'infecting' people, for lack of a better word. I need to know for a project I'm working on how do you call a creature like that. I've looked for weeks and found bubkes. any ideas?

Update: to be clear, I'm searching for information about creatures that reproduce this way. I'm not looking for a name to call them, I'm looking for the name they are known for. If you know about a creature that fits my description, please tell me in the comments.

Thank you.