Ebola virus is named for the Ebola River, which is the headstream of the Mongala River, a tributary of the Congo, or Zaire, River. The Ebola River empties tracts of rain forest, winding past scattered villages. The first known emergence of Ebola Zaire—the hottest type of Ebola virus—occurred in September 1976, when it erupted simultaneously in fifty-five villages near the headwaters of the Ebola River.
