Erabus Prime was a planet in the Gamma Quadrant

Erabus Prime was visited by Vash while in the company of Q. Vash was bitten by an insect on the planet that would have caused horrible sores to appear all over her body, were it not for Q's intervention.

The infection can be sub-divided into three stages. At the first stage, the patient loses most of his scalp hair, except for a few strands. During the second stage, oozing boils appear all over the body. Finally, during the third stage, the patient begins to shiver, is no longer able to walk and skin and hair turn gray. (DS9: "Q-Less")

Three stages of Erabus Prime bug infection
Stage 1: Loss of hair	Stage 2: Oozing Boils	Stage 3: Shivering and gray skin + hair