As of June 25, public health authorities have identified 296 persons with viral hemorrhagic fever (VHF) attributable to documented or suspected Ebola virus infection in an outbreak in the city of Kikwit and the surrounding Bandundu region of Zaire (1,2); 79% of the cases have been fatal, and 90 (32%) of 283 cases in persons for whom occupation was known occurred in health-care workers. This report summarizes characteristics of persons with VHF from an initial description of cases and preliminary findings of an assessment of risk factors for transmission.