Ebola Virus Essay Research Paper Please Read

Ebola Virus Essay, Research Paper

Please Read This Warning Before You Use This Essay for Anything (It Might Save Your Life) Ebola VirusThe Ebola Virus is the common name for several strains of virus, threeof which are known to cause hemorrhagic fever in humans, which ischaracterized by massive bleeding and destruction of internal tissues.Named for the Ebola River in Zaire, Africa, where the virus was firstidentified, the Ebola virus belongs to the family Filoviridae. Threestrains of Ebola virus that are often fatal to humans have beenidentified. Named for the areas in which the first recognized outbreakstook place, these strains are referred to as Ebola/Zaire (EBOZ),Ebola/Sudan (EBOS), and Ebola/Tai Forest (EBOT). A fourth Ebola strain,called Ebola/Reston(EBOR), has not been found to cause disease inhumans. As outbreaks of Ebola hemorrhagic fever continue to occur,other strains may be identified. The viruses are long rods, 800 to1000 nanometers (nm) long (1 nm equals one-billionth of a meter, or 4 x10-8 in), but particles as long as 14,000 nm have been seen. Each virusconsists of a coiled strand of ribonucleic acid (RNA) contained in anenvelope derived from the host cell membrane that is covered with 7 nmspikes placed 10 nm apart visible on the surface of the virion (Figure1). When magnified several thousand times by an electron microscope,these viruses have the appearance of long filaments or threads but theparticles are pleomorphic, meaning they can exist in many shapes. Theirbasic structure is long and filamentious, essentially bacilliform, butthe viruses often takes on a “U” shape (Figure 2). They contain aunique single-stranded molecule of noninfectious (negative sense ) RNA.The virus is composed of 7 polypeptides, a nucleoprotein, aglycoprotein, a polymerase and 4 other undesignated proteins. Proteinsare produced from polyadenylated monocistronic mRNA a speciestranscribed from vi genomes. As the infection progresses the cytoplasm of the infected celldevelops “prominent inclusion bodies” which contains the viralnucelocapsid, which will become highly structured. The virus thenassembles, and buds off the host cell, attaining its lipoprotein coatfrom the infected cell’s outer membrane. The replication in anddestruction of the host cell is rapid and produces a large number ofviruses budding from the cell membrane. Symptoms Cases of Ebola haveoccurred in isolated instances and in outbreaks in sub-Saharan Africa.A significant problem in diagnosing the disease is that the virusesoften strike in remote areas of developing countries, where access tolaboratories for specimen analysis is limited. Of all the Ebolastrains, Ebola/Zaire is the most dramatic and deadly. The Ebola viruscauses hemorrhagic fever, which is characterized by such symptoms assevere headache, weakness, and muscle aches, followed by vomiting,abdominal pain, diarrhea, inflammation of the throat (pharyngitis),inflammation of the mucous membranes in the eye (conjunctivitis), andbleeding from body openings. The virus spreads through the blood and isreplicated in many organs. The histopathologic change is focal necrosisin these organs, including the liver, lymphatic organs, kidneys,ovaries and testes. The central lesions appear to be those affectingthe vascular endothelium and the platelets. The resultingmanifestations are bleeding, especially in the muc usually seven to tendays. The mortality rates in the known outbreaks have been 60 percent with Ebola/Sudan virus and 77 to 88 percent with Ebola/Zairevirus. Although it is believed that death results directly from thedamage to internal tissues, it is not known why some patients manage tosurvive the disease. There are no proven therapeutic drugs to treatEbola hemorrhagic fever, and treatment currently consists of preventingshock and providing supportive care. Medical care is complicated by theneed to protect medical and nursing personnel. Convalescence is slow,often taking five weeks or more, and is marked by weight loss andamnesia in the early stages of recovery. Currently, there is littlehope of developing a vaccine against the Ebola virus. Near the end ofone outbreak in Zaire during 1995, blood from convalescent patients wastransfused into severely ill victims in an attempt to transferantibodies and T-lymphocytes (one type of white blood cell) that mightneutralize the Ebola virus and destroy infected cells. This proceduremet with some success, but carefully controlled trials must beconducted to confirm the safety and effectiveness of this method.Evolution Besides morphological and biochemical similarities, allnonsegmented negative-strand RNA viruses share several features intheir mechanisms of transcription and replication: similar genomeorganization, complementarity of the genome extremities, homologoussequences in the 3′ untranslated region, conserved transcriptionalsignals, interruption of genes by intergenic sequences, possession of avirion-associated polymerase, helical nucleocapsid as the functionaltemplate for synthesis of replicative and messenger RNA, replication bysynthesis of a full-length antigenome, transcription of messenger RNAsby sequential interrupted synthesis from a single promotor,transcription and replication in the cytoplasm, and maturation byenvelopment of independently assembled nucleocapsids at membrane sitescontaining inserted viral proteins. These data suggest that allnonsegmented negative-strand RNA viruses are derived from a commonprogenit