The Ebola Virus
A virus is an ultramicroscopic infectious organism that, having no independent metabolic activity, can replicate only within a cell of another host organism. A virus consists of a core of nucleic acid, either RNA or DNA, surrounded by a coating of antigenic protein and sometimes a lipid layer surrounds it as well. The virus provides the genetic code for replication, and the host cell provides the necessary energy and raw materials. There are more than 200 viruses that are know to cause disease in humans. The Ebola virus, which dates back to 1976, has four strains each from a different geographic area, but all give their victims the same painful, often lethal symptoms.
The Ebola virus is a member of a family of RNA viruses known as Filoviriade' and falling under one genus, Filovirus'. "The Ebola virus and Marburg virus are the two known members of the Filovirus family" (Journal of the American Medical Association 273: 1748). Marburg is a relative of the Ebola virus. The four strains of Ebola are Ebola Zaire, Ebola Sudan, Ebola Reston, and Ebola Tai. Each is named after the geographical location in which it was discovered. These filoviruses cause hemorrhagic fever, which is actually what kill victims of the Ebola virus. Hemorrhagic fever as defined in Mosby's Medical, Nursing, and Allied Health Dictionary as, a group of viral aerosol infections, characterized by fever, chills, headache, malaise, and respiratory or GI symptoms, followed by capillary hemorrhages, and, in severe infection, oliguria, kidney failure, hypotension, and, possibly, death. The incubation period for Ebola Hemorrhagic Fever ranges from 2-21 days (JAMA 273: 1748). The blood fails to clot and patients may bleed from injections sites and into the gastrointestinal tract, skin and internal organs (Ebola Info. from the CDC 2). The Ebola virus has a tropism for liver cells and macrophages, macrophages are cells that engulf bacteria and help the body defend against disease. Massive destruction of the liver is a hallmark feature of Ebola virus infection. This virus does in ten days what it takes AIDS ten years to do. It also requires biosaftey level four containment, the highest and most dangerous level. HIV the virus that causes AIDS requires only a biosaftey level of two. In reported outbreaks, 50%-90% of cases have been fatal (JAMA 273: 1748).
Ebola can be spread in a number of ways, and replication of the virus occurs at an alarming rate. Ebola replication in infected cells takes about eight hours. Hundreds to thousands of new virus particles are then released during periods of a few hours to a few days, before the cells die. The several cycles of replication occur in a primate before the onset of the fever and other clinical manifestations (Ornstein, Matthews and Johnson 7). In most outbreaks, transmission from patient to patient within hospitals has been associated within the reuse of unsterile needles and syringes. High rates of transmission in outbreaks have occurred from patients to heath-care workers and to family members who provide nursing care without appropriate precautions to prevent exposure to blood, other body fluids, vomitus, urine and stool. Risk for transmitting the infection appears to be highest during the later stages of illness, which are often characterized by vomiting, diarrhea, shock, and frequently hemorrhaging (JAMA 274: 374). Even a person who has recovered from the symptoms of the illness may have the virus present in the genital secretions for a brief period after. This makes it possible for the virus to be spread by sexual contact. Complete recovery is reached only when no particles of the virus are left in the body fluids, this however is rarely attained. The disease, for humans, is not airborne, capable to be passed on through air travel, but for nonhuman primates it has been a possibility in a few cases.
Ebola Zaire was identified in 1976 in Northern Zaire and...
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