A rare disease that kills within a day if untreated, survived by James Kirk and still carried in his blood, which the rulers of Gideon steal to bring death back to their overcrowded world.
Vegan choriomeningitis is central to the Original Series episode The Mark of Gideon. The illness brings high fever and pain in the arms and back and is fatal within about twenty-four hours without treatment. Kirk caught it earlier in his career and, though cured, still carries the organism.
The people of Gideon have become almost immune to death and their planet is unbearably crowded. Having learnt of Kirk's medical history, the council lures him to a replica of the Enterprise so that Odona, daughter of Ambassador Hodin, can be infected from his blood.
Odona falls ill as planned. McCoy cures her aboard the real Enterprise, and she returns home able to pass the disease to volunteers who wish to die and thin the population.