Ebola Virus
From Wikipedia, the free encyclopedia
Ebola is the common term for a group
of viruses belonging to genus Ebolavirus, family Filoviridae, and
for the disease which they cause, Ebola hemorrhagic fever. The
viruses are characterised by a long, filamentous morphology
surrounded by a 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.
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Virus classification
Group: Group V ((-)ssRNA)
Order: Mononegavirales
Family: Filoviridae
Genus: Ebolavirus
Type species
Zaïre Ebolavirus
Species
Reston Ebolavirus
Sudan Ebolavirus
Ivory Coast Ebolavirus
Bundibugyo Ebolavirus
Ebola
Classification & external resources
ICD-10 A98.4
ICD-9 065.8
DiseasesDB 18043
MedlinePlus 001339
eMedicine med/626
MeSH C02.782.417.415 |
Overview
The Ebola virus first emerged in 1976 in simultaneous outbreaks in
Sudan and Zaire. Ebola is considered to be the deadliest virus of
all time, but it is not as well known as Smallpox because Ebola
outbreaks have been limited mainly to remote areas of the world.
It is known to be a zoonotic virus as it is currently devastating
the populations of lowland gorillas in Central Africa. Despite
considerable effort by the World Health Organization, no animal
reservoir capable of sustaining the virus between outbreaks has been
identified. However, it has been hypothesized that the most likely
candidate is the fruit bat.
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
this particular 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.
Etymology
The virus is named after the Ebola River Valley in the African
nation-state of the Democratic Republic of the Congo (formerly Zaïre),
near the site of the first recognized outbreaks in 1976.
Size and shape
Electron micrographs of members of Ebolavirus show them to have the
characteristic thread-like structure of a filovirus. EBOV VP30 is
around 288 amino acids long. The virions are tubular and variable in
shape and may appear as a "U", "6", coiled, circular, or branched
shape, however, laboratory purification techniques, such as
centrifugation, may contribute to the various shapes seen. Virions
are generally 80 nm in diameter. They are variable in length, and
can be up to 1400 nm long. On average, however, the length of a
typical Ebola virus is closer to 1000 nm. In the center of the
virion is a structure called nucleocapsid, which is formed by the
helically wound viral genomic RNA complexed with the proteins NP,
VP35, VP30 and L. It has a diameter of 40 – 50 nm and contains a
central channel of 20–30 nm in diameter. Virally encoded
glycoprotein (GP) spikes 10 nm long and 10 nm apart are present on
the outer viral envelope of the virion, which is derived from the
host cell membrane. Between envelope and nucleocapsid, in the
so-called matrix space, the viral proteins VP40 and VP24 are
located. |
