Ebola overview

Overview
Ebola is the common term for a group of viruses belonging to genus Ebola, family Filoviridae, and for the disease which they cause, Ebola hemorrhagic fever. The viruses are characterised by a long, filamentous morphology surrounded by a protein/lipid viral envelope. Ebola viruses are morphologically similar to the Marburg virus, also in the family Filoviridae, and share similar disease symptoms. Ebola has caused a number of serious and highly publicized outbreaks since its discovery.

The virus is named after the Ebola River Valley in the Democratic Republic of the Congo (formerly Zaïre), near the site of the first recognized outbreak in 1976, in a mission run by Flemish nuns.

The Ebola virus first came to notice in 1976 in outbreaks of Ebola hemorrhagic fever in Zaire and Sudan. The strain of Ebola which broke out in Zaire has one of the highest case fatality rates of any human pathogenic virus, roughly 90%. The strain which broke out later in Sudan has a mortality of approximately 50%. The virus is believed to be initially transmitted to a human via contact with an infected animal host. From the first human infected, the virus is then transmitted by human contact with infected blood and bodily fluids of a diseased 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.

Ebola is believed to be a zoonotic virus as it is currently devastating the populations of lowland gorillas in Central Africa. As of late 2005, three species of fruit bat were identified as carrying the virus, and did not exhibit symptoms, and are now believed to be the natural host species, or reservoir, of the virus.

Ebola hemorrhagic fever is potentially lethal and encompasses a range of symptoms including fever, vomiting, diarrhea, generalized pain or malaise, and sometimes internal and external bleeding. Mortality rates are extremely high, with the human case-fatality rate ranging from 50% - 89%, according to viral subtype. The cause of death is usually due to hypovolemic shock or organ failure.

Because Ebola is potentially lethal and since no approved vaccine or treatment is available, Ebola is classified as a biosafety level 4 agent, as well as a Category A bioterrorism agent by the Centers for Disease Control and Prevention. It has the potential to be weaponized for use in biological warfare and was investigated for that use by both the Soviet Union and the United States during the Cold War. Its effectiveness as a biological-warfare agent is compromised by its extreme deadliness and its level of contagion: a typical outbreak spreads through a small village or hospital, affects the entire population, and then runs out of potential hosts, burning out before it reaches a larger community. Also important is that none of the strains of Ebola known to cause disease in humans have been found to be airborne; only the strain known as Ebola Reston (after the city of Reston, Virginia where it was first identified in Green Monkeys) is believed to be airborne.