Due to the stagnant swamps in which they live and their contact with the blood of numerous creatures, stirges are harbingers of disease. Any creature subjected to a stirge's blood drain attack has a 10% chance of being exposed to filth fever, blinding sickness, or a similar disease (Pathfinder RPG Core Rulebook 557). Once this check is made, the victim can no longer be infected by this particular stirge, though attacks by different stirges are resolved normally and may result in multiple illnesses.