Ebola hemorrhagic fever is one of the deadliest of a group of diseases called viral hemorrhagic fevers. They range in seriousness from relatively mild illnesses to severe and potentially fatal diseases. All forms of viral hemorrhagic fever begin with fever and muscle aches. Depending on the virus, the disease can get worse until the patient becomes very ill with breathing problems, severe bleeding (hemorrhage), kidney problems, and shock.

Viral hemorrhagic fevers are caused by viruses from four families: filoviruses, arenaviruses, flaviviruses, and bunyaviruses. The usual hosts for most of these viruses are rodents or arthropods (such as ticks and mosquitoes). In some cases, the natural host for the virus is not known.