Also known as Poke-AIDS. A sinister computer virus that infects pokemon gameboy games when certain cheats are used. In the red, blue, and yellow versions, infection is caused by capturing a pokemon over lv 100, capturing misingnode, and possibly encountering misingnode at all. In gold, silver, and crystal versions, infection is caused by cloning pokemon in the PC by switching their locations to another box and then turning off the game before it is saved. The virus spends a long time after it activates where it just sits in your game, doing nothing, but if you link with someone their game gets it. Eventually it destroys ALL data it the game.
Just one case of Pokemon AIDS can spread to infect hundreds of games before anyone notices anything.