Making Diseases Effective in Fantasy

Maybe "effective" isn't the exact word I'm looking for, but deadly diseases should be a society-wide threat and fear in faux-medieval fantasy, and in a world with readily available magical healing, that's just not the case.  I've handled that differently at times in my GURPS gameworld, but none of the solutions I've come up with have satisfied me.  I tried breaking down the standard Cure Disease spell into specific versions for different diseases, but that just leads to unnecessary bookkeeping.  The old standby "Mummy's Curse", wherein a disease is a curse and not really a disease, is another possibility, but it seems like in most games of GURPS I'm as likely to have PCs with the Remove Curse spell because the Curse spell is terrible.

My latest solution is having Magic-Resistant diseases, and making Cure Disease one-try.  So, for example, the Grey Death, which is often fatal and has Magic Resistance 10, can be a real threat to a society.  This seems to be the best one so far.  I think it's also appropriate for some diseases, especially "true" leprosy, to be Cure Disease immune.

Why the Focus On Disease?

I think it's reasonable to ask why I worry about this.  After all, no-one really wants to roleplay having cholera (roll 13 vs. HT 11: "OK, you poop yourself again and are Terribly Dehydrated.")  For me, it's more a question of world-building than the actual gameplay.  My gameworld is definitely late medieval Europe in inspiration, and even a cursory read of the time period should give you an idea of how constant and present the threat of disease was. Some, like leprosy, were a terror from the biblical age on.  To have a universal panacea like Cure Disease really changes the tone away from what I'm looking for.  Plus, while I don't want to constantly affect the PCs with nasty sicknesses, they should occasionally face an actual threat from it.