The desiseTheroy

One theroy Which in a way dose not link with the others but in a way dose. Is the theroy that vampires are just people with a disese that affects there blood and to live they need to replace that blood regually. In the this theroy was in the Film Blade in which the dises affected the bloods ability to carry hymoglobyn (which carries oxygen)

IF vampires did exsist then this would be the only realisic cause that abides by law of physics and other stuff we know. it is also posible that this could also go along with all the other theroys in that people who had the disese formed the clans.