Corprus, meaning skin blight in Ald Chimeris, is in Morrowind a name used for any of a number of ailments affecting the skin. The Dunmer are especially susceptible to skin blights for reasons unclear to healers. They range from mild annoyances to destructive plagues that can lead to disfigurement or death. Corprus maladies can have natural and unnatural causes. Natural corprus afflictions are caused by unsanitary conditions, unbalanced humors and parasites. Examples of such natural afflictions include inflammation, discoloration, the flaking and sloughing of corrupted flesh, or an outbreak of blisters or ulcerations. During the Interregnum, a house healer dedicated to studying corprus afflictions found that the best method for avoiding most corprus blights is to bathe often, wear clean clothes, and consume clean, pure food.
Unnatural causes of corprus blights include those of magical or alchemical nature. One such example is the Flay Blight of 2E 565, wherein hundreds of Dark Elves on the western shore of Vvardenfell contracted rashes that caused irritated, blotchy skin. The Flay Blight was caused by a change to the alchemical formula of a popular face cream of the time.
During the Third Era, the term "corprus" became especially associated with the so-called Divine Disease, which was the most terrible of the ailments associated with the Blight. The infection was created by Dagoth Ur and spread by contact with a corprus beast or by a specific curse. It destroys the mind of the sufferer and grotesquely deforms the body. It is not known how the transformation of Sixth House cultists into Ascended Sleepers and other monsters is related to Corprus. Some of the physical effects are similar, but the cultists remain lucid and attain a higher spiritual state whereas more mundane sufferers become mindless husks, like the common undead raised by necromancers.
Perhaps the most frightening aspect of this form of corprus is that it is completely incurable. Those infected were sent to Tel Fyr to live in the Corprusarium, where they were treated and studied by Divayth Fyr, a 4000-year old wizard working to uncover the nature of the disease and create a cure. Fyr had a theory that the Divine Disease is in fact not a disease, but rather a divine blessing that most mortals can't handle, pointing to the fact that the victims are completely immune to other diseases and don't age.
The last known Dwemer, Yagrum Bagarn, was infected with corprus atop Red Mountain during his exploration of Tamriel. He sought refuge at the Corprusarium in Tel Fyr, where he offered his knowledge and provided theories on the disappearance of the Dwarves.
In 3E 427 the Nerevarine became infected with corprus, and Divayth Fyr provided a "cure" for the disease. This "cure" did not actually cure the disease but rather removed the negative effects, such as crippling physical deformities and insanity, while retaining the positive effects, including immunity to all diseases, increased strength and endurance, and possibly also immortality.
Yagrum Bagarn, the last Dwemer, who was infected by Corprus
For game-specific information, see the Morrowind article.