(Quick bit of nastiness for you direct from my phone's note pad of D&D ideas to develop. Hope you like this rather unusual - mechanics speaking - disease)
EFFECT: At the end of each extended rest, the victim makes a D.C. 19 Endurance check. Failure means the number of Healing Surges they have is reduced by one until they are cured.
If they would be reduced to 0 Healing Surges (when they die), or die whilst infected with this disease, they rise 1 minute later as a Zombie.
SYMPTOMS: Fever, shaking, nightmares, hallucinations, hunger (once half surges have been reached, this is for blood and raw meat. Each time a creature is first wounded within line of sight of the victim, they must make a saving throw or be dazed (save ends) as they wrestle with their hunger.), clammy skin, sweating, stridor, death, reanimation.