Key Facts about Ebola virus disease

Ebola virus disease (EVD), formerly known as Ebola haemorrhagic fever,
is a severe, often fatal illness in humans.

EVD outbreaks have a case fatality rate of up to 90%.
EVD outbreaks occur primarily in remote villages in Central and West
Africa, near tropical rainforests.

The virus is transmitted to people from wild animals and spreads in
the human population through human-to-human transmission.
Fruit bats of thePteropodidaefamily are considered to be the natural
host of the Ebola virus.

Severely ill patients require intensive supportive care. No licensed
specific treatment or vaccine is available for use in people or
animals.

Ebola first appeare d in 1976 in 2 simulta neous outbrea ks, in
Nzara, Sudan, and in Yambuk u, Democr atic Republic of Congo.
The latter was in a village situated near the Ebola River, from
which the disease takes its name.

Genus Ebolavir us is 1 of 3 member s of the Filovirid ae family
(filoviru s), along with genus Marburg virus and genus Cuevavir
us. Genus Ebolavir us compris es 5 distinct species:
1.Bundibugyo ebolavirus (BDBV)
2.Zaire ebolavirus (EBOV)
3.Reston ebolavirus (RESTV)
4.Sudan ebolavirus (SUDV)
5.Taï Forest ebolavirus (TAFV).

BDBV, EBOV, and SUDV have been associat ed with large EVD
outbrea ks in Africa, whereas RESTV and TAFV have not. The
RESTV species, found in Philippi nes and the People's Republic of
China, can infect humans, but no illness or death in humans from
this species has been reporte d to date.

Transmission
Ebola is introduc ed into the human populati on through close
contact with the blood, secretio ns, organs or other bodily
fluids of infected animals. In Africa, infectio n has been docume
nted through the handlin g of infected chimpan zees, gorillas,
fruit bats, monkey s, forest antelop e and porcupi nes found ill
or dead or in the rainfore st.

Ebola then spreads in the commu nity through human- to-huma n
transmi ssion, with infectio n resultin g from direct contact
(throug h broken skin or mucous membra nes) with the blood,
secretio ns, organs or other bodily fluids of infected people, and
indirect contact with environ ments contami nated with such
fluids. Burial ceremo nies in which mourne rs have direct
contact with the body of the decease d person can also play a
role in the transmi ssion of Ebola. Men who have recover ed
from the disease can still transmit the virus through their
semen for up to 7 weeks after recovery from illness.

Health- care workers have frequent ly been infected while treating
patients with suspecte d or confirm ed EVD. This has occurre d
through close contact with patients when infectio n control
precauti ons are not strictly practiced.

Among workers in contact with monkey s or pigs infected with
Reston ebolavir us, several infectio ns have been docume nted in
people who were clinically asympto matic. Thus, RESTV appears
less capable of causing disease in humans than other Ebola
species.

Howeve r, the only availabl e evidenc e availabl e comes from
healthy adult males. It would be prematu re to extrapol ate the
health effects of the virus to all populati on groups, such as
immuno - comprom ised persons, persons with underlyi ng medical
conditio ns, pregnan t women and children. More studies of RESTV
are needed before definitiv e conclusi ons can be drawn about
the pathoge nicity and virulenc e of this virus in humans.

Signs and symptoms
EVD is a severe acute viral illness often characte rized by the
sudden onset of fever, intense weakne ss, muscle pain, headach
e and sore throat. This is followe d by vomitin g, diarrhoe a,
rash, impaire d kidney and liver function , and in some cases,
both internal and external bleedin g. Laborat ory findings
include low white blood cell and platelet counts and elevated
liver enzyme s.

People are infectio us as long as their blood and secretio ns
contain the virus. Ebola virus was isolated from semen 61
days after onset of illness in a man who was infected in a
laborato ry.

The incubati on period, that is, the time interval from infectio
n with the virus to onset of sympto ms, is 2 to 21 days.