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Ebola overview

Published: July 16, 2009. Updated: August 09, 2009

Ebola hemorrhagic fever (EHF; commonly referred to as simply Ebola) is a recently identified, severe, often fatal infectious disease occurring in humans and some primates caused by the Ebola virus.

The Ebola virus was first discovered in 1976, and since its discovery, different strands of Ebola have caused epidemics with 50 to 90 percent mortality in Zaïre, Gabon and Uganda.

The Ebola virus

The Ebola virus comes from the Filoviridae family, similar to the Marburg virus. It is named after the Ebola River in Zaïre, Africa, near where the first outbreak in 1976 after a significant outbreak in Yambuku, Zaire (now the Democratic Republic of the Congo), and Nzara, in western Sudan. Of 602 identified cases, there were 397 deaths.

The two strains identified in 1976 were named Ebola-Zaire (EBO-Z) and Ebola-Sudan (EBO-S). The outbreak in Sudan showed a lower fatality rate (50%) compared to the 90% mortality rate of the Zaire strain. In 1990, a second, similar virus was identified in Reston, Virginia amongst monkeys imported from the Philippines, and was named Ebola-Reston.

Further outbreaks have occurred in Zaire/Congo (1995 and 2003), Gabon (1994, 1995 and 1996), and in Uganda (2000). A new subtype was identified from a single human case in the Côte d'Ivoire (Ivory Coast) in 1994, EBO-CI.

Of around 1500 identified Ebola cases, two-thirds of the patients have died. The animal (or other) reservoir which sustains the virus between outbreaks has not been identified.

Ebola hemorrhagic fever

Among humans, the virus is transmitted by direct contact with infected body fluids such as blood. The cause of the index case is unknown.

The incubation period of Ebola hemorrhagic fever varies from two days to four weeks. Symptoms are variable too, but the onset is usually sudden and characterized by high fever, prostration, myalgia, arthralgia, abdominal pains and headache. These symptoms progress to vomiting, diarrhea, oropharyngeal lesions, conjunctivitis, organ damage (notably the kidney and liver) by co-localized necrosis, proteinuria, and bleeding both internal and external, commonly through the gastrointestinal tract. Death or recovery to convalescence occurs within six to ten days.


No specific treatment has been proven effective, and no vaccine currently exists. A vaccine is in the developmental stages. Ebola is known to exist in humans and a few monkey species can be infected. To develop the vaccine, monkeys are used but it can not be tested on humans except in outbreak environments so the vaccine must be tested extensively and meet strict government regulations. Also, in the development of a vaccine, accessibility and cost for people of poor nations and the transportation efficiency of it must be considered.


Although there is no specific treatment for patients with Ebola, there have been entire books written about how to prevent it from spreading from the patient to health care workers or other patients. The first step in prevention is to make advanced preparations for Ebola and other viral hemorrhagic fevers (VHFs). Selecting a VHF Coordinator to oversee preparations for VHF activities, such as the following, does this:

Serving as the focal point for information and leadership when a VHF case is suspected.
Informing all health facility staff about VHFs and the risks associated with them.

Organizing training in VHF Isolation Precautions for staff that will work with VHF patients or infectious body fluids.

Making sure that teams are trained to prepare and transport bodies for burial (CDC 115-116).
The next step is maintaining a minimum standard of cleanliness in the hospital. This includes washing hands and sterilizing needles (CDC 9-18). Also, the medical staff must be informed about the different types of VHFs, including Ebola, and their symptoms. Symptoms that are common to many VHFs are severe weakness and fatigue, and a fever for more than 72 hours and less than three weeks. The patient also may have unexplained bleeding from the mucous membranes, skin, eyes, or gastrointestinal tract. The patient may also be going into shock (has a blood pressure of less than 90 mm Hg or a rapid weak pulse). Finally, that patient may have had contact with someone in the last three weeks that had an unexplained illness with fever or bleeding or who died with an unexplained severe illness with a fever (CDC 23).

The next thing to do is isolate the patient from other patients who may get sick and health care workers who are not directly involved with the patient's care. The patient should be given intravenous support, as he or she is probably dehydrated from losing fluids through vomiting and diarrhea. Finally, if the patient expires, the body should be properly disposed of, preferably through cremation, so that the dead body will not spread disease to other people (CDC 26).

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