BAMAKO, Mali ? It all started with a sick nurse, whose positive test for Ebola came only after her death. In a busy clinic that treats Mali's elite as well as wounded U.N. peacekeepers, what patient transmitted the virus? Soon hospital officials were taking a second look at the case of a 70-year-old man who died after being brought to the capital late at night from Guinea suffering from kidney failure. A friend who visited him later died under suspicious circumstances, too. It wasn't renal disease, they then realized. The 70-year-old man had Ebola and all three of the relatives who brought him to the...