My idea:
An epic vampire lord by the name of Cyros, through centuries of effort, managed to find and put together the Cross of Blood, an artifact created in ancient times that some believe are responsible for the creation of the first vampires.
The powers of the cross of blood are unknown, but apparantly Cyros was able to use the cross to change how the curse of vampirism affected him. Cyros was the grandchild of a silver dragon-human mating, and in addition to being enhanced in various ways above and beyond a normal vampire, Cyros is now able to infect humanoids, monstrous humanoids, AND dragons.
Cyros has already successfully managed to surprise and convert 5 adult dragons of various colors into vampires which he has made his lieutenants, and Cyros and the 5 were able to convert a great gold wyrm by the name of Auruk, who has become Cyros's general.
Several dozen smaller dragons have been attacked and converted by the might of Cyros, Auruk and their minions, and already there is talk among the dragons of stopping this plague before it begins. It is rumored a paladin and his silver dragon lover attempted to slay Cyros but only managed to get them both converted into vampires.
Richard M.
Grimfang"Whisper"Xaeraes