[RPG] What happened to disease in D&D 5e


In the Player's Handbook, disease is mentioned in the Petrified condition's description ('the creature is immune to poison and disease'), but there is no Diseased condition to be found, nor is disease even listed in the book's index. Is the idea that every disease is unique and so there is no 'general' condition to cover it?

Best Answer

Based on the appearance of disease in the Otyugh entry (HotDQ supplment, p. 14) and the publication history of D&D, it's a fair bet that diseases will be defined in an ad hoc manner rather than systematised. Only a couple editions define diseases in a "disease system" way, and the editions that 5e is giving hat-tips to don't do that, instead opting to cover diseases by giving them simple, unique game and fictional effects defined where relevant.

We've already seen this ad hoc methodology in the Player's Handbook as well, with the spell contagion defining its own diseases. The trend seems to point firmly toward not prescribing a core mechanic for diseases and the overall game's design not needing one anyway, instead leaving them to be defined by their definition — much like spell effects are, in fact.

Based on that, we can expect new diseases to be simple and largely defined in three places:

  1. The DMG (pp.256-257)--includes a few "standard" diseases that are common, may recur across a number of monsters and adventures, and are recommended for baselines from which to create homebrew diseases
  2. The entries for monsters that inflict diseases other than those covered by the DMG already
  3. Adventures that feature unique or new diseases (in line with the expected DMG's "diseases do what the designer/DM say" guidelines), except where already defined by the MM or DMG

This is how disease was treated in many editions. It allowed for simplicity and clarity of effects without descending into tangles of rules interactions, and gave DMs flexibility in creating new diseases to suit homebrewed monsters and settings. It worked very well, and is in-line with the general return to simple rules stated simply that D&D 5e is showing.

Pushing disease into the DMG, and defining them in an ad hoc way instead of within a known "disease mechanic" or system, also allows for a wider variety of play styles to be supported: disease effects can be shared with players if the DM's aim is, e.g., for them to be a mechanical challenge or puzzle; or kept hidden and only revealed through narrative description if the DM's aim is, e.g., for diseases to be frightful unknowns that require seeking medical help to diagnose and cure.