Ebola hemorrhagic fever, also called Ebola virus disease, is caused by a virus of the family Filoviridae, genus Ebolavirus. Discovered in 1976, Ebola virus was named for a river in Zaire, Africa, where it was first detected. The source of the Ebola virus in nature remains unknown, although the fruit bat is suspected to be the natural reservoir. In an attempt to identify the source, investigators have tested thousands of animals captured near outbreak areas, but their efforts have been unsuccessful. Monkeys and gorillas, like humans, appear to be susceptible to infection and, if infected, may serve as a source of the virus.
Outbreaks of this disease have appeared sporadically, in Central and Western Africa, since the first occurrence in 1976. During each of these outbreaks, a majority of cases occurred in hospital settings under the challenging conditions of the developing world. These conditions, including a lack of adequate medical supplies and the frequent reusing of needles and syringes, played a major role in the spread of the disease. Outbreaks were more easily controlled when appropriate medical supplies and equipment were available and quarantine procedures were used.
The incubation period, the period between becoming infected and showing symptoms, is two to 21 days. Initial symptoms may include fever, chills, headaches, muscle aches and loss of appetite. As the disease progresses, vomiting, diarrhea, abdominal and chest pain, and sore throat can occur. Patients may suffer liver or kidney damage, and may bleed from injection sites or into the gastrointestinal tract, skin and internal organs.
Ebola virus is spread through contact with blood and other body fluids of a person ill with the disease. In outbreaks of Ebola, person-to-person transmission frequently occurs among health care workers or family members who care for an ill person. The virus also has been spread through the reuse of hypodermic needles in the treatment of patients. Reusing needles may be a common practice in developing countries, where the health care system is underfinanced. U.S. medical facilities do not reuse needles.
Patients with Ebola virus are able to spread the disease once symptoms develop, but the virus does not spread during the incubation period when symptoms are not present. However, the virus may be present in the genital secretions of such persons for a brief period after their recovery; therefore, it is possible for the virus to be spread through sexual contact.
Diagnosis is made by detecting Ebola antigens (antigen detection tests), antibodies (ELISA) or genetic material (PCR, electron microscopy, serum neutralization tests) or by culturing and isolating the virus from clinical specimens. These specimens usually have been treated to inactivate (kill) the virus. Research on Ebola virus must be done in a special high-containment laboratory to protect scientists working with infected tissue.
In the United States, laboratory testing for Ebola hemorrhagic fever is done at the Centers for Disease Control and Prevention (CDC). All clinical specimens collected for Ebola virus testing are an extreme biohazard risk, and testing must be conducted according to BioSafety Level-4 guidelines.
Patients infected with Ebola are given supportive therapy. Fluids are given to replace those lost due to vomiting and diarrhea, medication can be given to lower fever, and the patient’s blood pressure and oxygen are closely monitored. Antibiotics can be given to prevent secondary bacterial infections. Vaccines and treatments for Ebola are being developed and tested, but none have been approved for use.
Previous outbreaks of Ebola hemorrhagic fever have been successfully controlled by isolating patients. This is done through a method called "barrier technique," which entails the following actions: 1) doctors and nurses wear gowns, masks, gloves and goggles when caring for patients; 2) the patient's visitors are restricted; 3) disposable materials are removed from the room and burned after use; 4) all reusable materials are sterilized before reuse; and 5) all hard surfaces are cleaned with a sanitizing solution, since the virus is easily destroyed by disinfectants.
Persons in the United States are at risk only if they have had contact with blood or body fluids from patients who are ill and infected with Ebola virus. There is a possibility that an infected, symptomatic patient could arrive in the United States via plane. In this situation, the patient would be isolated upon arrival to prevent further transmission of the virus. The risk to fellow travelers is low, but persons should avoid contact with blood and secretions of ill individuals. Travelers to areas experiencing an Ebola outbreak should be aware of travel advisories and restrictions. Travelers should avoid handling ill or dead animals and should avoid ill persons unless they are a health care provider using appropriate infection control practices.
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