Myrruthesia

Myruuthesia was a pecuiliar disease that could infected Vulcan's 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 Star Empire and the Federation at war as the Romulans desperately attempted to reach Canara; home to a special compound that could synthesize a cue for the disease. (TOS novel: Web of the Romulans)