As of May 26, 2005, the Angolan Ministry of Health had reported 399 cases of Marburg hemorrhagic fever, 335 of which were fatal. Even as this unprecedented spread of filovirus infection continued, Marburg's sister virus, Ebola, had killed nine people in the Republic of Congo. Although Ebola may now be the better-known sibling, Marburg virus was identified first, in 1967, after an infectious-disease clinician at the university hospital in Marburg, Germany, saw patients with a severe febrile syndrome associated with bleeding from multiple sites on the skin and the mucous membranes and shock. The patients all worked for a pharmaceutical manufacturer, and it later became evident that they had acquired their infection from African green monkeys that were used in the preparation of cell cultures for vaccines. The virus that was isolated in these cases was totally unrelated to any known virus family and turned out to have such a large, bizarre, branching morphology (see diagram ) that initially many were even uncertain that it was a virus.