This is a newly invented term and could be subject to change
The mystery plague that killed 99% of all the usual inhabitants of the world in which your story is set. Since NPCs are so hard to implement properly, the usual IF shortcut is to somehow make the world mostly deserted. Sometimes it's a literal plague. Abandonitis is hard to avoid completely, but try to make your world seem just a little lived in, even if there's nobody home right now. Finding an absent character's diary is a stock feature of Abandonitis.
- Situations where you would normally expect to find people (a shop, an office, a school) are inexplicably empty or have contrived explanations for the lack of inhabitants
- The game is set entirely in a post-apocalyptic scenario - ruins, rubble, deserted bases
- You find one or more diaries of absent characters
Reasons to Use
- Fully implemented NPCs take a lot of work to get right. Removing their direct presence from the story and moving them 'offstage', only seen through their artifacts or writings, can paradoxically make them more vivid and interesting.
- Traditionally IF has cast the player in the role of explorer of ruined/abandoned realms, so this is carrying on a classic theme
- The standard IF libraries in most modern systems make implementing this kind of game easy, so you should start with the story that best fits your toolset.
- In IF, unlike a roleplaying game, the player really is interacting with an absent human via an artifact - the game program - so why not make the underlying metagame/subtextual structure of the player/author conversation a feature?
Reasons to Avoid
- It's been done so many times before
- IF should have as a goal to emulate the forms of linear fiction genres, most of which include human interaction as a significant story component
- It's hard to keep coming up with new and convincing reasons for the absence of people
- Some of the most interesting development in IF at the moment is in simulating conversations and human interaction, so you should deliberately try to include plausible human characters to push the boundaries of what's achievable