Ebola hemorrhagic fever (ORPHA:319218)
Ebola hemorrhagic fever (EHF), caused by Ebola virus, is a severe viral hemorrhagic disease characterized by initial fever and malaise followed by gastrointestinal symptoms, bleeding, shock, and multi-organ system failure.
Epidemiology
EHF is seen in Central and West Africa. EHF is generally recognized only when there are outbreaks, usually of less than 100 cases, which are almost invariably fueled by nosocomial transmission in hospitals in resource-poor areas where proper infection control practices are not maintained. However, seroprevalence studies suggest unrecognized endemic transmission in some areas of Africa.
Clinical description
After an incubation period of about 8 days (range 3-21 days), patients typically present with the abrupt onset of non-specific signs and symptoms including fever, malaise, headache, chest pain, and myalgia/arthralgia, followed rapidly by gastrointestinal symptoms (vomiting, diarrhea, abdominal pain) and, in some cases, a maculopapular skin rash. Severe cases develop bleeding (sub-conjunctival hemorrhage, epistaxis, bleeding from the mouth and rectum, oozing from venipuncture sites), neurologic involvement (disorientation, convulsions, coma), shock, and multi-organ system failure. Mild-to-moderate leukopenia and thrombocytopenia are often present and disseminated intravascular coagulation (DIC) commonly develops, best indicated by the presence of D-dimers.
Etiology
Over 25 different viruses cause viral hemorrhagic fever. Ebola virus is a member of the virus family Filoviridae, along with Marburg virus. Six different species of Ebola virus have been identified to date, although only four are pathogenic to humans, all of which are endemic only in sub-Saharan Africa. Accumulating evidence implicates fruit bats as the Ebola virus reservoir, with primary human infection occurring presumably from unwitting contact with bat excreta or saliva. Infection also occasionally occurs through contact with tissues of other wild primates, especially gorillas and chimpanzees, presumably also infected through bat exposure. Human-to-human transmission occurs through direct contact with blood or bodily fluids of infected persons.
Diagnostic methods
Common diagnostic modalities include cell culture (restricted to biosafety level-4 laboratories), serologic testing by enzyme linked immunosorbent assay (ELISA) or indirect fluorescent antibody (IFA), and RT-PCR. Because no commercial assays are presently available, these tests are typically performed only in a few specialized laboratories.
Differential diagnosis
EHF is difficult to distinguish from a host of other febrile illnesses, at least early in the course of disease. Other viral hemorrhagic fevers need to be excluded, especially Marburg hemorrhagic fever, as well as malaria, typhoid fever, leptospirosis, rickettsial disease (see these terms) and meningococcemia.
Management and treatment
Patients should be isolated and viral hemorrhagic fever precautions (face shields, surgical masks, double gloves, surgical gowns, and aprons) should be used to prevent nosocomial transmission. As there is presently no antiviral drug available for EHF, treatment is supportive, following the guidelines for treatment of severe septicemia. Persons who had unprotected contact with someone with EHF should be monitored.
Prognosis
Case fatality rates vary consistently with the specific infecting virus, ranging from zero to over 80%. Shock, bleeding, neurological manifestations, high viremia, AST > 150 IU/L, and pregnancy confer a poor prognosis. Although convalescence may last up to a year, survivors usually have no lasting sequelae.

                            Last update: 
                            December 2012


                            - Expert reviewer(s): 
                            Dr Daniel BAUSCH  -  Andrew BENNETT