107,600 years ago, a Giant Brain entity was exposed to the viral agent and contracted Akwood's syndrome. This entity lived within the core of an inhabited, ringed, class M asteroid. Although the indigenous humanoid population were not infected, the Giant Brain transmitted its own bouts of insanity into the inhabitants, driving them temporarily insane for 100 millennia.
In 2267, the USS Enterprise beamed down a landing party to explore the surface of this asteroid. Geologist Freyer became infected with Akwood's syndrome when he tasted a soil sample. The virus had mutated and grown millions of times larger within the brain entity. Kirk, McCoy and Freyer transported directly into the Giant Brain, lured the pathogens into a concentrated area and then delivered the antidote, which killed the virus and cured the Giant Brain of Akwood's syndrome. (TOS comic: "The Brain-Damaged Planet")