Diseased is a condition added in the Second Edition base game.
Condition text: At the start of your turn, test 
. If you pass, discard this card or token. If you fail, suffer 1 
and keep this card or token.
Creatures who are diseased must test at the start of their turns. If they pass, the Diseased condition is discarded. If they fail, 1 is suffered and the condition remains on that creature.
Zombies are frequently associated with the Disease condition. Other monsters that can inflict this status are the Ferrox, Plague Worm, and the Carrion Drake. Other Disease sources for the heroes are the Infector class for the Overlord and the Bol'Goreth Plot Deck.
Front side.
Back side.