The Ice Sickness

In 871, a disease called the Ice Wraith Fever spread from the north in Garthspire to the other two nations. It started with cold sweats and chills before moving into a deep cough that led to a "fog" slipping from the diseased's mouth. The magical virus was thought to have come from an unearthed tomb during one of the many expeditions there, and was brought back with the explorers and researchers. It had an incubation period of nearly a month, so figuring out who was a carrier for the disease and who was not, or its source, was nearly impossible. It lasted almost 12 years and wiped out a third of the population