In 5e, poisons, disease, curses, etc. ALL fucking suck because they're incredibly easy to remove. That sucks because it deprives the DM of some powerful and interesting narrative tools. As is, there's almost no point in using those kind of conditions because players literally remove them almost instantly. Sure the DM can create one that the players can't remove as easily, but that just pisses the players off and creating a 'tough' every time you need it is just cringe and contrived.
To fix that I set the precedent that ALL afflictions are much more challenging to remove. My players loved this. In fact, in the past, none of them had any fear of those conditions and considering getting cursed, poisoned, or diseased to be more annoying than threatening.
So here is what I did about it.
This is a copy/paste from my houserules document.
Disease and Poisons (updated)
Many, many types of disease and poison exist throughout Faerun.
Most afflictions can be diagnosed and treated, but not necessarily before they become symptomatic and manifest in illness, but others are so incredibly rare or dangerous that little is known about them.
After first contact with a disease, it will typically develop over 3-5 stages that worsen as it progresses. Each stage can last between a few days to several weeks. However, some afflictions manifest much more quickly and can mature in a matter of hours, minutes, or even seconds.
As previously mentioned, some forms diseases have no detectable symptoms in the early stages of progression and, unfortunately, as a disease progresses it typically become more difficult to treat. Additionally, once cured, the after-effects can sometimes persist until the individual has time to rest and recuperate.
Poison, on the other hand, typically manifests much more quickly than a disease and the symptoms are, generally, more serious.
Magic, such as Lesser Restoration, can cure many ailments, but spells that remove afflictions require a spell 'attack' roll against the DC of the disease or poison. It is also important to note that particularly virulent diseases (and poisons) may require multiple successful casts to remove the affliction. Furthermore, there are afflictions that also require specific spell components that must be used in conjunction with restorative magics to cure the affliction.
• Curative spells of levels 1-4 make their 'attack' (cure) rolls normally and rolls that are >= to the DC of the affliction count as one successful cast.
• Curative spells of levels 5-7 make their 'attack' (cure) rolls with Advantage and rolls that are >= to the DC count as two successful casts
• Curative spells of level 8-9 remove any disease, poison, or curse except those imposed by an exceptionally powerful source or entity (typically CR 25+).
For example – Eddie has Black Fever (DC 14) which requires 1 success to remove. So, Eddie has paid a Cleric to cure the disease. The Cleric casts Lesser Restoration which has no standard attack roll, but for the sake of diseases (and poisons) we can easily calculate one.
The Cleric casting the Lesser Restoration spell is level 3 (+2 proficiency bonus) and has a Wisdom of 15 (+2 WIS modifier) so the Cleric has a +4 to his Lesser Restoration 'attack' (cure) roll.
The Ceric would need to roll a 10 or higher to remove the Black Fever (DC 14). Given that Lesser Restoration is a level 1-4 spell, the spell receives no modifier to its roll and a 'hit' counts as one success which is enough to remove Eddie's Black Fever.
As you can see, disease and poisons have the potential to be serious problem. Particularly, in cases where the DC of the virulent affliction is high and requires multiple successful uses of curative magic. The difficulty is further compounded if the affliction requires a specific material component.
However, expanding the scope of afflictions make them far more interesting and allow groups to engage in meaningful narrative events rather than effectively hand-waving potentially dangerous situations with a simple cast of Lesser Restoration. While that can still happen, it's no longer a forgone conclusion.
Curses
Curses exist in many forms. There are the classically cursed items all the way to physical manifestations like Vampirism, Lycanthropy, or worse. Curses and cursed items are not always easily remedied with a simple cast of Remove Curse which may only suppress the curse temporarily. Some curses are much stronger and require exhaustive measures in order to remove them permanently.
Removing a curse functions in almost exactly the same way that curing a disease or poison does. The curse's DC must be beaten by a spell 'attack' roll and some curses require multiple successes in order to be removed. Particularly dangerous curses can require specific types of weather, regions, locations, etc in addition to the necessary magic and material components.
