It probably affects all the spire owners, as well as the Necroveils. I can only assume it's the same for the Seelie court and the important members of it, since it isn't just us that are infected.

As far as I know, no one has bee able to get rid of it yet; there are assumptions about what cures could be, but I haven't actually talked to anyone that has gotten rid of it. I don't think it's anything so easily beaten, unfortunately; I tried using curative magic on it, which lessened it for a little while, before the silver returned like I hadn't tried the magic on it at all. Whatever it is, it doesn't seem like magic can actually fight back against it in a way that would be a permanent fix to the illness.