Myruuthesia was a disease peculiar to Vulcans and their cousin species, the Romulans. It was considered generally very rare and communicable only in its early stages.
In the 23rd century, a deadlier and more virulent strain of myrruthesia struck the Romulan Star Empire and devastated a third of the population who would die within forty-eight hours should a cure not be administered. This nearly brought the Empire and the Federation at war as the Romulan ship Raptor desperately attempted to reach Canara, which was home to a special compound that could synthesize a cure for the disease. (TOS novel: Web of the Romulans)