Ebola virus (EBOV)
causes acute severe haemorrhagic fever leading to up to 90% lethality.
Increasingly frequent outbreaks and the placement of EBOV in the
category A list of potential biothreat agents have boosted interest in
this virus.
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Filovirus
The disease
closely resembles Marburg virus disease. Ebola Virus Disease has a
high mortality.
Furthermore,
development of new technologies (e.g. reverse genetics systems) and
extensive studies on Ebola haemorrhagic fever (EHF) in animal models
have substantially expanded the knowledge on the pathogenic mechanisms
that underlie this disease.
Two major factors
in EBOV pathogenesis are the impairment of the immune response and
vascular dysfunction.
Ebola virus
infection was first recognized during a human outbreak in 1976 with
almost simultaneous outbreaks in both the Sudan and Zaire (now the
Democratic Republic of the Congo). It was named after a river in the
Democratic Republic of the Congo.
The Ebola virus
is now known to have four subtypes : Zaire, Sudan, Reston, and Ivory
Coast .
After an outbreak
in 1979 in the Sudan, Ebola appeared relatively quiescent until it
appeared among macaque monkeys imported from the Philippines and
housed at a primate facility in Reston, Virginia.
In late 1994, a
single case in a researcher who performed a necropsy on an ill
chimpanzee led to the identification of a new subtype, Ebola-Ivory
Coast.
In Gabon,
Africa, outbreaks of Ebola virus infection occurred from 1994 to 1997.
Another appearance was in 2000-2001 with an Ebola outbreak in Uganda
that resulted in 425 cases with 224 deaths by January 2001. In this
outbreak, events and conditions associated with acquired disease were
: funeral attendance for those who died with Ebola hemorrhagic fever,
intrafamilial contact, and nosocomial infections. Schools were closed
and a ban against funerals was enacted.
In November,
2001, an Ebola outbreak again occurred in Gabon. and in the Democratic
Republic of the Congo, and multiple outbreaks occurred in 2000-2004 in
Gabon, the Congo, Sudan, and Uganda. Outbreaks continue in the Congo
in 2005. At the same time, it was noted that Ebola outbreaks occurred
in large mammals, mainly chimpanzees, duikers (a type of antelope),
and gorillas, and that human outbreaks tended to follow those observed
in animals. Airborne transmission of the Ebola Zaire strain to monkeys
by aerosol has been demonstrated but is not known to occur from
human-to-human. To date, no animal reservoir for Ebola virus has been
identified.
Although the natural host and the route
of transmission are uncertain, the ebola virus appears to be spread
mainly by close and prolonged contact with an infected person or by
inoculation from contaminated syringes and needles.
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Marburg Virus Disease
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