hypothetical "worst possible disease" that someone could get. usually used to describe how one feels physically. Symptoms of this fake disease usually change depending on the creativity of the people who define those symptoms.
John: Hey want to go do something tonight?
Kate: Nah man, I'm pretty sure I have Zombie AIDS. I feel terrible! I feel like my stomach is melting on the inside and my limbs are probably going to fall off. Damn Zombie AIDS...