A is for Aphasia virus. DS9 was struck by one in 2369. B is for Ba'ltmasor Syndrome. A Klingon malady. C is for Clarke's Disease. It killed Henry Archer. D is for Denebian Fever. E is for Epidural Hematoma. Chekov had one. F is for Freighter blight. Scourge of Malon officers. G is for Gorch. H is for Hyperthyroidism. Artificially induced by Dominion genetic engineering. I is for Ivonian flu. J is for Jean Luc Picard who suffered from Irumodic Syndrome later in life. K is for Kalla-Nohra Syndrome. Caused at Gallitep by inhalation of toxic gas. L is for the Levodian flu, a mutated strain of which became airborne in the mid-22nd century and infected millions of Klingons, causing their head ridges to disappear and their appearance to become more humanlike. M is for Melkotian Mumps. N is for numb tongue. O is for Orion Pheromonal Fever. P is for Phage. Q is for quadrotriticale blight. R is for Rigellian Kassaba Fever. S is for Scalosian Scabies. T is for the Tellurian Plague, one of the most virulent and dangerous epidemics known to 24th century Federation science. U is for Ulian Flu. V is for Vulcan Pon Farr. If it can kill you; it's a disease. Probably genetic.