Symbalene blood burn is a deadly disease that can kill a human in a few minutes, and wipe out a population of a billion people in a week or more. The pathogen causes the the vascular lining to literally boil away. Initial symptoms include a critical rise in body temperature and blood pressure, followed by extreme pain in the extremities and the rupture of capillaries. (TOS: "The Changeling", ENT: "Cold Station 12")
Samples of Symbalene blood burn were stored at Starfleet's Cold Station 12 for study. In 2154, a group of Augments led by Arik Soong exposed one of the doctors there to Symbalene blood burn in an effort to force Dr. Jeremy Lucas to give them the access codes for the stored Augment embryos. (ENT: "Cold Station 12")
In 2370, Reginald Barclay thought that he perhaps had Symbalene blood burn after Dr. Beverly Crusher assured him that he did not have Terellian Death Syndrome. (TNG: "Genesis")