Orion blood fever

Orion blood fever is a particularly virulent disease that originated from the planet Orion.

An outbreak of this disease ravaged settlements on Rigel VII in 2270. (FASA RPG: Star Trek IV Sourcebook Update.)
 * The timeline in the Star Trek IV Sourcebook Update mentioned that several Klingon settlements were depopulated due to the outbreak. However, Rigel VII was shown to be the home of the barbaric Kaylar in the TOS pilot "The Cage."