Very little is known about the spores that cause what is commonly called infestation. Some citizens appear to be immune to the effects of the spores, while others fall victim with surprising speed. Others appear to be only partially immune, showing signs of infestation, but being able to resist the influence of the spores (see information on Symbiants).
Once completely infested, a victim is totally under control of the resen and begins to work at one with the will of the spores, working to spread the affliction further across the world. Who or what controls the infested as a whole remains unknown, although there is lots of speculation.
Although once found in the east, resen spores have been largely eliminated from that area, due to the strict quarantine that has been in place for many years.