There are some diseases on Gor, and Dar-Kosis is one of them, however, it must be noted that this disease seems to afflict only  a few, it is not an epidemy. I
would not consider  dar-kosis an incurable disease, more like a bane to the the Initiates.


On Dar-Kosis

Dar-kosis is a virulent, horrible, wasting disease and is similar in many ways to leprosy. "Suddenly to my horror, I saw the quarry of the larl, It was a human
being, moving with surprising alacrity over the rough ground. To my astonishment, I saw it wore the yellow cerements of the sufferer of Dar Kosis, that
virulent, incurable, wasting disease of Gor." Tarnsman of Gor, page 149
Once, however, Talena dragged me to the side of the road, and scarcely able to conceal our horror, we watched while a sufferer from the incurable Dar-kosis
disease, bent in his yellow shrouds, hobbled by, periodically clacking that wooden device which warns all within hearing to stand clear of his path. 'An Inflicted
One,' said Talena, gravely, using the expression common for such plagued wretches on Gor. The name of the disease itself, Dar-kosis, is almost never
mentioned. I glimpsed the face beneath the hood and felt sick. It's one bleary eye regarded us blankly for a moment, and then the thing moved on.  
Tarnsmen of Gor, page 113


"For many years," said Flaminius, "and this was even before 10,110, the year of Pa-Kur and his horde, I and others worked secretly in the Cylinder of
Physicians. We devoted our time, those Ahn in the day in which we could work, to study, research. Test and experiment unfortunately, for spite and for gold,
word of our work was brought to the High Initiate, by a minor Physician discharged from our staff for incompetence. The Cylinder of Initiates demanded that
the High Council of the Caste of Physicians put an end to our work, not only that it be discontinued but that our results to that date be destroyed. The
Physicians, I am pleased to say, stood with us. There is little love lost between Physicians and Initiates, even as is the case between Scribes and Initiates.
Assassin of Gor, page 266

Some," said Flaminius. "Already some eight, of skill and repute, have pledged themselves my aids in this undertaking." He looked at me. "And the first, who
gave courage to them all," said he, "was a woman, of the Caste of Physicians, once of Treve."

"A woman named Vika?" I asked.

"Yes," said he, "do you know her?"

"Once,"' said I.

"She stands high among the Physicians of the city," he said.

"You will find her, I think," I said, "brilliantly worthy as a colleague in your work." Assassin of Gor, page 398

“No,” said Flaminius, smiling. “No.” He took another swallow. “I thought to find,” said he, “an immunization against Dar-Kosis.”
“Dar-Kosis is incurable,” I said.
“At one time,” said he, “centuries ago, men of my caste claimed age was incurable. Others did not accept this and continued to work. The result was the
Stabilization Serums.”
Dar-Kosis, or the Holy Disease, or Sacred Affliction, is a virulent, wasting disease of Gor. Those afflicted with it, commonly spoken of simply as the Afflicted
Ones, may not enter into normal society. They wander the countryside in shroudlike yellow rags, beating a wooden clapping device to warn men from their
path; some of them volunteer to be placed in Dar-Kosis pits, several of which lay within the vicinity of Ar, where they are fed and given drink, and are, of
course, isolated; the disease is extremely contagious. Those who contract the disease are regarded by taw as dead.
“Dar-Kosis,” I said, “is thought to be holy to the Priest-Kings, and those afflicted with it to be consecrated to Priest-Kings.”
“A teaching of Initiates,” said Flaminius bitterly. “There is nothing holy about disease, about pain, about death.” He took another drink.
“Dar-Kosis,” I said, “is regarded as an instrument of Priest-Kings, used to smite those who displease them.”
“Another myth of Initiates,” said Flaminius, unpleasantly.
“But how do you know that?” I queried.
“I do not care,” said Flaminius, “if it is true or not. I am a Physician.”
“What happened?” I asked.
“For many years,” said Flaminius, “and this was even before 10,110, the year of Pa-Kur and his horde, I and others worked secretly in the Cylinder of
Physicians. We devoted our time, those Ahn in the day in which we could work, to study, research, test and experiment. Unfortunately, for spite and for gold,
word of our work was brought to the High Initiate, by a minor Physician discharged from our staff for incompetence. The Cylinder of Initiates demanded that
the High Council of the Caste of Physicians put an end to our work, not only that it be discontinued but that our results to that date be destroyed. The
Physicians, I am pleased to say, stood with us. There is little love lost between Physicians and Initiates, even as is the case between Scribes and Initiates.
The Cylinder of the High Initiate then petitioned the High Council of the City to stop our work, but they, on the recommendation of Marlenus, who was then
Ubar, permitted our work to continue.” Flaminius laughed. “I remember Marlenus speaking to the High Initiate. Marlenus told him that either the Priest-Kings
approved of our work or they did not; that if they approved, it should continue; if they did not approve, they themselves, as the Masters of Gor, would be
quite powerful enough to put an end to it.” Assassin of Gor, page 265-266

Bazi Plague

Bazi plague is a deadly, rapidly spreading disease with no known cure. Its symptoms include pustules which appear all over the body, and a yellowing of the
whites of the eyes. "The Physician would check the health of the crew and slaves, Plague some years ago had broken out in Bazi, to the North, which port
had been closed by the merchants for two years. In some eighteen months it had burned itself out, moving south and eastward. Bazi had not yet recovered
from the economic blow." Explorers of Gor, page 117.

Pox

The tall man crouched down beside us, irritably. One of the men with him wore the green of the physicians. The tall man looked at us. As naked female slaves
we averted our eyes from his. I smelled the straw.
“Wrist-ring key,” said the tall man.
The merchant handed him the key that would unlock the wrist rings.
“Leave the lamp and withdraw,” said the tall man. The short merchant handed him the lamp and, frightened, left the room.
The men crouched down and crowded about the auburn-haired girl. I heard them unlock one of her wrist rings.
“We are going to test you for pox,” he said. The girl groaned. It was my hope that none on board the Clouds of Telnus had carried the pox. It is transmitted
by the bites of lice. The pox had appeared in Bazi some four years ago. The port had been closed for two years by the merchants. It had burned itself out
moving south and eastward in some eighteen months. Oddly enough some were immune to the pox, and with others it had only a temporary, debilitating
effect. With others it was swift, lethal and horrifying. Those who had survived the pox would presumably live to procreate themselves, on the whole
presumably transmitting their immunity or relative immunity to their offspring. Slaves who contracted the pox were often summarily slain. It was thought that
the slaughter of slaves had had its role to play in the containment of the pox in the vicinity of Bazi.
Later...
I understood then they were not concerned with the pox, which had vanished in the vicinity of Bazi over two years ago. Slave Girl of Gor, page 325 - 326
This research is done on the series of books written by John Norman, the comments in italics are mine and my point of view.
Woman of Gor
All rights reserved.
Caste of Physicians
Diseases on Gor
More on the lives of the Green Caste-Physicians of Gor
In this section, I have added comments to some quotes, it is my own point of view
reflected in the comments, it is what i  understand from reading the boooks and
studying each aspects of gorean life.