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Ebola Virus Ebola Virus
by The Ovi Team
2016-06-27 10:24:24
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27th June 1976; the world’s first recorded Ebola virus epidemic begins making its way through the area. By the time the epidemic is over, 284 cases are reported, with about half of the victims dying from the disease.

ebola01_400Ebola is the virus Ebolavirus (EBOV), a viral genus, and the disease Ebola hemorrhagic fever (EHF), a viral hemorrhagic fever (VHF). The virus is named after the Ebola River Valley in the Democratic Republic of the Congo (formerly Zaire), which is near the site of the first recognized outbreak in 1976 at a mission hospital run by Flemish nuns. It remained largely obscure until 1989 when several widely publicized outbreaks occurred among monkeys in the United States.

The virus interferes with the endothelial cells lining the interior surface of blood vessels and with coagulation. As the blood vessel walls become damaged and destroyed, the platelets are unable to coagulate, patients succumb to hypovolemic shock. Ebola is transmitted through bodily fluids, while conjunctiva exposure may also lead to transmission. There are five recognized species within the ebolavirus genus, which have a number of specific strains. The Zaire virus is the type species, which is also the first discovered and the most lethal. Electron micrographs show long filaments, characteristic of the Filoviridae viral family.

The genera Ebolavirus and Marburgvirus were originally classified as the species of the now-obsolete Filovirus genus. In March 1998, the Vertebrate Virus Subcommittee proposed in the International Committee on Taxonomy of Viruses (ICTV) to change the Filovirus genus to the Filoviridae family with two specific genera: Ebola-like viruses and Marburg-like viruses. This proposal was implemented in Washington, D.C., as of April 2001 and in Paris as of July 2002. In 2000, another proposal was made in Washington, D.C., to change the "-like viruses" to "-virus" resulting in today's Ebolavirus and Marburgvirus.

Rates of genetic change are one hundred times slower than Influenza A in humans, but on the same magnitude of that of Hepatitis B. Using these rates, the Ebolavirus and Marburgvirus are estimated to have diverged several thousand years ago. However, paleoviruses (genomic fossils) of filoviruses (Filoviridae) found in mammals indicate that the family itself is at least tens of millions of years old.

Ebolavirus first emerged in 1976 in outbreaks of Ebola hemorrhagic fever in Zaire and Sudan. The strain of Ebola that broke out in Zaire has one of the highest case fatality rates of any human pathogenic virus, roughly 90%, with case-fatality rates at 88% in 1976, 59% in 1994, 81% in 1995, 73% in 1996, 80% in 2001–2002, and 90% in 2003. The strain that broke out later in Sudan has a case fatality rate of around 50%. The virus is believed to be transmitted to humans via contact with an infected animal host. The virus is then transmitted to other people that come into contact with blood and bodily fluids of the infected person, and by human contact with contaminated medical equipment such as needles. Both of these infectious mechanisms will occur in clinical (nosocomial) and non-clinical situations. Due to the high fatality rate, the rapidity of demise, and the often remote areas where infections occur, the potential for widespread epidemic outbreaks is considered low.

Proceedings of an International Colloquium on Ebola Virus Infection and Other Hemorrhagic Fevers were held in Antwerp, Belgium, on December 6 through December 8 in 1977. While investigating an outbreak of Simian hemorrhagic fever (SHFV) in November 1989, an electron microscopist from USAMRIID discovered filoviruses similar in appearance to Ebola in tissue samples taken from Crab-eating Macaque imported from the Philippines to Hazleton Laboratories Reston, Virginia. Due to the lethality of the suspected and previously obscure virus, the investigation quickly attracted attention.

Blood samples were taken from 178 animal handlers during the incident. Of those, six animal handlers eventually seroconverted. When the handlers failed to become ill, the CDC concluded that the virus had a very low pathogenicity to humans. Philippines and the United States had no previous cases of infection, and upon further isolation it was concluded to be another species of Ebola or a new filovirus of Asian origin, and named Reston ebolavirus (REBOV) after the location of the incident.


     
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