An incurable disease released by the Dominion on a Gamma Quadrant world as punishment for defiance, infecting every inhabitant from birth and eventually killing them in an agonising final stage.
The blight is seen in the Deep Space Nine episode The Quickening. Two centuries before, the people of a prosperous planet resisted the Dominion, and the Jem'Hadar destroyed their cities and infected the population. Everyone is born with blue lesions; when the lesions turn red the victim has quickened and will die in pain within days.
Society has collapsed around the disease. The most respected man in the settlement is Trevean, who gives poison to those who quicken so that they can die peacefully. Bashir, sure that he can find a cure, discovers too late that the fields from his instruments make the virus mutate and kill his patients sooner.
He fails to cure the blight, but his treatment of the pregnant Ekoria means her child is born free of it, giving the next generation a vaccine.