EBOLA

virus (family Filoviridae) responsible for a severe and often fatal hemorrhagic fever; outbreaks in primates as well as in humans have been recorded. The disease is characterized by extreme fever, rash, and profuse hemorrhaging. Fatality rates range from 50 to 90 percent. The virus takes its name from the Ebola River in northern Congo (Kinshasa), where it first emerged in 1976. Outbreaks that year in what was then Zaire and in The Sudan resulted in hundreds of deaths, as did another outbreak in Zaire in 1995. Ebola is closely related to the Marburg virus, which was discovered in 1967, and the two are the only members of the Filoviridae, designated a family in 1987. Viewed through an electron microscope, the Ebola virus appears as long filaments, sometimes branched or intertwined. The virion (virus particle) contains one molecule of noninfectious, single-stranded RNA (ribonucleic acid). How the Ebola virus attacks cells is not known; however, it has been postulated that the virus produces proteins that suppress the immune system, allowing reproduction of the virus to continue unhindered. Viral hemorrhagic fevers like Ebola typically are carried by arthropods and rodents; however, the natural reservoir for the Ebola virus has yet to be discovered. Ebola can be transmitted through contact with infected blood, semen, body fluids, and possibly urine and respiratory secretions. The virus has also been detected in the organs of patients after recovery from the fever. Unsanitary conditions and lack of adequate medical supplies have been a factor in the spread of the disease. The Ebola virus has an incubation period of 4 to 16 days. The onset is sudden and harsh. Infected persons develop fever, severe headaches and muscle aches, and loss of appetite. Within a few days the virus causes a condition known as disseminated intravascular coagulation. This condition is marked by both blood clots and hemorrhaging. In the case of Ebola fever, clots are concentrated in the liver, spleen, brain, and other internal organs, forcing capillaries to bleed into surrounding tissue. Nausea, vomiting and diarrhea with blood and mucus, conjunctivitis, and sore throat soon follow. A maculopapular rash (discoloured elevations of the skin) appears on the trunk and quickly spreads to the limbs and head. The patient is then beset by spontaneous bleeding from body orifices and any breaks in the skin, such as injection sites, and within the gastrointestinal tract, skin, and internal organs. Death is usually brought on by hemorrhaging, shock, or renal failure and occurs within 8 to 17 days. There is no known treatment for Ebola fever. Current therapy consists of maintenance of fluid and electrolyte balance and administration of blood and plasma to control bleeding. The spread of the virus can be contained by barrier nursing, handling of infected blood and tissue in isolated laboratory units, and proper decontamination of reusable equipment.