Friday, May 27, 2016
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Characteristics of the virus
Ebola virus belongs to the order Mononegavirales and the family Filoviridae, which is a taxonomic group of non-segmented, enveloped and negative-strand RNA viruses. Particles of these viruses have a characteristic filamentous appearance that gives the virus family its name. Their diameter is uniform at 80 nm, but particle length can be quite variable and up to 14 000 nm.The genome of the virus consists of seven genes that code for nucleoprotein, glycoprotein, virion protein (VP) 24, VP30, VP35, VP40 and RNA-dependent RNA polymerase. With the exception of the glycoprotein gene, all aforementioned genes are monocistronic, which means that they encode for only one structural protein.
Production of a soluble glycoprotein (i.e. protein that contains covalently attached sugar residues) is an important distinction of Ebola virus from other viruses in the order. This major pathogenicity factor gets secreted from infected cells in large quantities, facilitating further viral entry by binding to the receptor present on the host cells.
According to the newest taxonomy of The International Committee on Taxonomy of Viruses (ICTV), in the genus Ebolavirus there are five recognized species: Zaire ebolavirus, Sudan ebolavirus, Taï Forest ebolavirus (formerly Côte d’Ivoire ebolavirus), Bundibugyo ebolavirus and Reston ebolavirus. Reston ebolavirus is the only species apathogenic for humans.
Ebola is caused by
infection with a virus of the family Filoviridae, genus Ebolavirus. There are five identified Ebola virus species, four of which are known to cause disease in humans: Ebola virus (Zaire ebolavirus); Sudan virus (Sudan ebolavirus); Taï Forest virus (Taï Forest ebolavirus, formerly Côte d’Ivoire ebolavirus); and Bundibugyo virus (Bundibugyo ebolavirus). The fifth, Reston virus (Reston ebolavirus), has caused disease in nonhuman primates, but not in humans.
Ebola viruses are found in several African countries. Ebola was first discovered in 1976 near the Ebola River in what is now the Democratic Republic of the Congo. Since then, outbreaks have appeared sporadically in Africa.
The natural reservoir host of Ebola virus remains unknown. However, on the basis of evidence and the nature of similar viruses, researchers believe that the virus is animal-borne and that bats are the most likely reservoir. Four of the five virus strains occur in an animal host native to Africa.
People get Ebola through direct contact (through broken skin or mucous membranes in, for example, the eyes, nose, or mouth) with
blood or body fluids (including but not limited to urine, saliva, sweat, feces, vomit, breast milk, and semen) of a person who is sick with or has died from Ebola,
objects (like needles and syringes) that have been contaminated with body fluids from a person who is sick with Ebola or the body of a person who has died from Ebola,
infected fruit bats or primates (apes and monkeys), and
possibly from contact with semen from a man who has recovered from Ebola (for example, by having oral, vaginal, or anal sex)
