When a character contracts a disease -- by being injured by a contaminated attack (such as a mummy's slam attack, which can transmit mummy rot), touches an item smeared with diseased matter, or consumes disease-tainted food or drink -- he must make an immediate Fortitude saving throw. If he succeeds, the disease has no effect -- his immune system fought off the infection. If he fails, he takes damage after an incubation period. Once per day afterward, he must make a successful Fortitude saving throw to avoid repeated damage. Two successful saving throws in a row indicate that he has fought off the disease and recovers, taking no more damage.
Diseases have various symptoms and are spread through a number of vectors.
Use of the Heal skill will remove the disease upon a successful DC check of 15. However, it will not remove any ability score damage resulting from the disease's effect. [edit] Recuperative spells are needed to repair ability score damage caused by disease.
Ability score drains caused by disease are only cured by a (lesser or better) Restoration spell or Cure Disease. Resting does nothing for it.