Ebola Virus Infection

One of the most frightening viruses to come out of the African subcontinent, the Ebola virus first appeared in 1976. More than 400 people in Zaire and the neighboring Sudan were killed by the hemorrhagic fever that it caused. Ebola virus has been responsible for several outbreaks in the years since then, including one that occurred in Zaire in the summer of 1995.

An unclassified ribonucleic acid (RNA) virus, Ebola is morphologically similar to the Marburg virus. Both viruses cause headache, malaise, myalgia, and high fever, progressing to severe diarrhea, vomiting, and internal and external hemorrhage.

Four strains of the Ebola virus are known to exist: Ebola-Zaire, Ebola-Sudan, Ebola-Ivory Coast, and Ebola-Reston. All four types are structurally similar, although they have different antigenic properties. However, Ebola-Reston causes illness only in monkeys, not in humans as do the other three.

The prognosis for Ebola virus infection is extremely poor, with mortality as great as 90%. The incubation period ranges from 2 to 21 days.

Causes

Ebola virus infection is caused by an RNA virus that is passed from person to person by direct contact with infected blood, body secretions, or organs. Nosocomial and community-acquired transmission can occur. Contaminated needles can also cause the infection. Transmission through semen may occur up to 7 weeks after clinical recovery. The virus remains contagious even after the patient has died.

Diagnostic tests

Specialized laboratory tests reveal specific antigens or antibodies and may show the isolated virus. As with other types of hemorrhagic fever, tests also demonstrate leukopenia as early as the first day, with leukocyte counts as low as 1,000/µl and neutrophilia by the fourth day. In addition, atypical lymphocytes and neutrophils with Pelger Hüet anomaly may appear, along with thrombocytopenia with fewer then 10,000 cells/µl between days 6 and 12. Hypofibrinogenemia and microangiopathic hemolytic anemia may also be evident.

Treatment

No cure exists for Ebola virus infection; treatment consists mainly of intensive supportive care. Administration of I. V. fluids helps offset the effects of severe dehydration. The patient may receive replacement of plasma heparin before the onset of clinical shock.

Experimental treatments include administration of plasma that contains Ebola virus-specific antibodies. Although this treatment has resulted in diminished levels of the Ebola virus in the body, further evaluation is needed.

Throughout treatment, the patient should remain in isolation. If diagnostic tests indicate that the patient is free from the virus - which typically occurs 21 days after onset in those few who survive - the patient can be released.

Prevention

Avoid areas of epidemics. Absolute gown, glove, and mask precautions are necessary around sick patients. These precautions will greatly decrease the risk of transmission.