Heh, that little section is actually based after Mummy Rot.As a side note, what's the point of casting remove curse? It seems like you have to succeed on a caster level check in order to bypass future caster level checks.
Basically the way I read it is that you can cure it in the following steps.
#1. Cast Break Enchantment or Remove Curse. You must make an opposed caster level check against the original caster.
#2. If successful you can now heal the disease with normal disease-getting-rid-of spells and need not make any further caster level checks.
How about if I make it so that anyone who makes the save becomes temporarily immune to the disease for a time?It is still damn powerful. As several others have stated this thing could take out whole nations, and it is only a 9th level spell. Something that can wipe out an entire civilization deserves to be a bit more powerful then Power Word Kill, which while nice, can hardly alter reality in the way this spell would.
Edit: Adjusted to the above.