Brian Lumley 
Necroscope V: Deadspawn 

High tide in a sea of blood!…And for Harry Keogh, Necroscope, the tide has finally turned. Always the champion of the living and the dead alike, now Harry is shunned by all men. Always a hunter of the evil that stalks the night, now he in turn is hunted. Always the hero, now he is the plague-bearer, the menace – the monster!But yet his greatest battle will be with himself, with the Thing Inside. For the Necroscope is now a vampire. Forsaken by the teeming dead pursued by the espers of E-Branch, Harry has a choice: to be banished, hounded right out of this world…or to release the plague which he carries within himself upon all humanity!