You should do something about that cough...

The last of the supplement rules where I'd sort of like to see some equivalent in Swords & Wizardry, aside from artifacts and sages, is disease rules. This is another area where Blackmoor and the Dungeon Masters Guide both have guidelines. The DMG's is much more general - area effected, chronic or acute, and severity - while Blackmoor gives guidelines for realistic diseases such as grippe (flu), cholera, typhus, malaria, the bubonic plague, and so on.

The older system is by far the better. It presents each disease with what is likely to carry it - so you'd actually have flea-bitten plague rats, you'd be more likely to get malaria or yellow fever in a mosquito-infested swamp, typhus during a siege, cholera or dysentery from bad water, tuberculosis in a city, and so on.

I've long felt that disease rules were frequently neglected, despite being constantly on the edge of utility in the game. You have Cure Disease and Disease spells, cursed scrolls cause disease, giant rats have a chance to give you diseases, and you're walking around in an underground world that has to have some nasty germs and so forth in it. But I think it's not seen as "heroic" enough to have disease rules; after all, what good is a fighter if they just get typhus and die in a siege?

But in the real world, by far the biggest killer during wars before the 20th century was disease. In no small part this is because wars were mostly composed of marching, camping and sieges, with a few pitched battles at key moments. So to me at least, it's interesting to have some good disease rules, and I think in part the rarity of the Blackmoor supplement hurt things, since its simple and interesting rules got lost in the shift to AD&D.

One very interesting fact about Blackmoor is its treatment of Cure Disease. Several diseases state outright that you only catch them once: you never get a second bout of the black plague, and you're only at risk to die of dysentery the first time, for instance. But Cure Disease doesn't remove the possibility; you haven't fought off the illness, it was just removed, and you can be susceptible to it again. Of course a further Cure Disease would work, but it makes for an interesting dynamic: taking a risk with a particular disease can get you immunity from it thereafter.

Another fascinating one is that a character who dies of leprosy can't be raised using Raise Dead. Considering that the rules give it to mummies, it makes them absolute terrors, able to cause a meaningful permanent death. Grippe, on the other end of the spectrum, is only fatal 2% of the time and is suggested as the opposite of Cure Light Wounds. I love the idea of an anti-cleric being able to touch a PC and give them the flu.

I do think a good set of herbalism rules alongside Blackmoor-style disease rules would make for a great pseudo-medieval disease set-up: characters get sick and often go to wise healers rather than just clerics. The right herbs and so on should enhance the survival roll, sometimes significantly. Likewise, things such as Bless spells and various superstitious rituals should lower the chances of actually contracting disease.

One aspect that the Blackmoor and DMG rules never touch on is demihumans. I think that it's much more interesting if elves and dwarves are immune to some diseases, hyper-sensitive to others, and have special diseases that humans can't get. For instance, a wasting disease among elves that causes them to raise as banshees or a fungus found deep in mines that absorbs and takes over dwarven flesh is a way to put a fantastic twist on this. Constitution likewise should come into play in survival.

I think that the rules we pick show what we're interested in. Disease rules show that you want to have a grittier fantasy world, in a very low fantasy register. They're heavily implied in the D&D rules, and I think that ignoring them (as many groups did and do) is one of the things that pushes the game into a high fantasy mode. This is true of a lot of the less popular subsystems in the older editions, which reinforced a particular vibe that the game's creators enjoyed but players looking for D&D to be Lord of the Rings or later epic fantasy did not.