A malignant theonoma:
1) It acts on the brain, reducing any capacity for rational thought
2) It secretes toxins which demand that the theonoma be stimulated at least weekly. This stimulation is generally in the form of close association with others who are likewise affected, and produces endorphins which leave the sufferer with a state of euphoria.
3) Severe cases lead to an overwhelming desire to infect as many people as possible, to increase the periodic stimulation and resulting endorphin release

From the comment thread of this post.