* Bulk of cases in Guinea, Liberia, Sierra Leone * Total includes new cases in Mali, U.S. * WHO warns that Ebola coming closer to Ivory Coast GENEVA, Oct 25 (Reuters) - The death toll from the Ebola epidemic rose to 4,922 out of 10,141 known cases in eight countries through Oct. 23, the World Health Organization (WHO) said on Saturday. The virus, which reached Mali through a two-year-old girl who died on Friday, now threatens Ivory Coast, having infected people virtually all along its borders with Guinea and Liberia. Ivory Coast is the world's biggest cocoa producer.