Durum sickness is a disease that afflicted the people of the Kingdom of Taforashia about 10 years before the events of Slayers REVOLUTION. This particular infection was caused by Rezo the Red Priest.
Other kingdoms promised aid and supplies to the beleaguered populace to treat the disease, but it was stolen by Gioconda and never reached the people. Rezo put the king and people of the country into suspended animation until a cure could be found. It was developed at some point over the next ten years, but could not be administered to the people of Taforashia because Rezo could not be found to awaken them; this was because of his transformation into Rezo-Shabranigdu and destruction at the hands of Lina Inverse. In Slayers EVOLUTION-R, Rezo's spirit is transferred into the body of Posel Korba Taforashia through the use of Hellmaster's Jar and he revives the people of Taforashia so the disease can at last be cured.