The Ebola virus, or Ebola, is a virus that causes a viral hemorrhagic fever (VHF). Ebola hemorrhagic fever (EHF) is a highly lethal blood disorder that caused an 89% mortality rate in the Democratic Republic of the Congo, formerly known as Zaire, from December 2002 to April 2003. Rapid recognition of symptoms of Ebola is essential in order to immediately start quarantine and supportive therapy. The most common symptoms of Ebola include a severe headache, fever with or without chills, muscle or joint pain, poor appetite, and asthenia or a general feeling of weakness.
Along with the Marburg virus, Ebola is a virus that belongs to the Filoviridae family. When a human or primate is infected, the Ebola virus replicates rapidly in all tissues, leading to cell necrosis. The most damaging necrosis occurs in the liver. When the host's immune system is overwhelmed by the infection, a fatal course ensues, and the host's blood and tissues contain large amounts of virus. In particular, body fluids and skin have large numbers of virions, thus serving as highly infectious transmission channels even when the host is already dead.
There are five known species of the Ebola virus. These include Ebola Zaire virus (EBO-Z) or Ebola Zaire virus (ZEV), Ebola virus in Sudan (EBO-S) or Ebola virus in Sudan (SEV), Ebola virus in Costa Ivory Coast (EBO-C) or Ivory Coast Ebola Virus (CIEV), Ebola Bundibugyo Virus (EBO-B) or Ebola Bundibugyo Virus (BEV), and Ebola Reston Virus (EBO-R) or the Reston Ebola virus (REV). They all cause human infection, but only the first four cause EHF. The main indicator of Ebola infection is a history of travel or work in places where Ebola is endemic, such as Sudan, the Democratic Republic of Congo, Ivory Coast, and Gabon. A history of travel to African tropical forests or exposure to an Ebola outbreak also increases the risk of EHF.
The symptoms of Ebola hemorrhagic fever depend on the stage of the disease. Initially, an infected person experiences fever, inflammation of the pharynx or pharyngitis, joint pain, and muscle pain. Around the fifth day of infection, a maculopapular rash appears, usually more prominent on the trunk. Many patients also complain of bilateral conjunctivitis or eye pain. Gastrointestinal conditions, including nausea and vomiting, abdominal pain, and diarrhea, also occur in association with bleeding in the gastrointestinal tract.
Among those who are fatally infected, an important sign is obtundation, which is decreased mental alertness and decreased response to pain. At this late stage, spontaneous bleeding from the mucous membranes is common. This is followed by lack of urine, increased respiratory rate, low blood pressure, and shock. Myocarditis and pulmonary edema are also seen. Patients often die while in a coma.