Twenty years ago Ebola virus first emerged in simultaneous outbreaks in Sudan and Zaire. Two following outbreaks have occurred, but transmission among human populations has not been sustained. Despite considerable progress in our understanding of Ebola we have not identified its natural reservoir or the trigger for its re-emergence in new outbreaks in humans. The World Health Organization had reported 114 cases of Ebola infection and 79 deaths in a new outbreak centered in Kikwit, a rural town of 400,000 situated in Bandundu Province, Zaire, ....