The ebola virus is shown in this undated electron micrograph photo provided by the U.S. Centers for Disease Control and Prevention in 1995. The ebola virus first was identified in Sudan and in a nearby region of Zaire (now Democratic Republic of the Congo) in 1976 after large epidemics in Yambuku, northern Zaire, and Nzara, southern Sudan.

Ebola hemorrhagic fever is one of the most virulent viral diseases known to humankind, causing death in 50 percent to 90 percent of all clinically ill cases. Several different species of ebola virus have been identified. The virus is transmitted by direct contact with blood, body fluids and tissues of infected people. The virus also has been transmitted through handling ill or dead infected chimpanzees. (© AP Images)