Key facts
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 the Pteropodidae family 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.
Transmission
Ebola is introduced into the human population
through close contact with the blood, secretions,
organs or other bodily fluids of infected animals.
In Africa, infection has been documented through
the handling of infected chimpanzees, gorillas,
fruit bats, monkeys, forest antelope and
porcupines found ill or dead or in the rainforest.
Ebola then spreads in the community through
human-to-human transmission, with infection
resulting from direct contact (through broken
skin or mucous membranes) with the blood,
secretions, organs or other bodily fluids of
infected people, and indirect contact with
environments contaminated with such fluids.
Burial ceremonies in which mourners have direct
contact with the body of the deceased person
can also play a role in the transmission of Ebola.
Men who have recovered from the disease can
still transmit the virus through their semen for up
to 7 weeks after recovery from illness.
Health-care workers have frequently been
infected while treating patients with suspected or
confirmed EVD. This has occurred through close
contact with patients when infection control
precautions are not strictly practiced.
Among workers in contact with monkeys or pigs
infected with Reston ebolavirus, several
infections have been documented in people who
were clinically asymptomatic. Thus, RESTV
appears less capable of causing disease in
humans than other Ebola species.
However, the only available evidence available
comes from healthy adult males. It would be
premature to extrapolate the health effects of the
virus to all population groups, such as immuno-
compromised persons, persons with underlying
medical conditions, pregnant women and
children. More studies of RESTV are needed
before definitive conclusions can be drawn about
the pathogenicity and virulence of this virus in
humans.
Signs and symptoms
EVD is a severe acute viral illness often
characterized by the sudden onset of fever,
intense weakness, muscle pain, headache and
sore throat. This is followed by vomiting,
diarrhoea, rash, impaired kidney and liver
function, and in some cases, both internal and
external bleeding. Laboratory findings include
low white blood cell and platelet counts and
elevated liver enzymes.
People are infectious as long as their blood and
secretions contain the virus. Ebola virus was
isolated from semen 61 days after onset of
illness in a man who was infected in a
laboratory.
The incubation period, that is, the time interval
from infection with the virus to onset of
symptoms, is 2 to 21 days.
Diagnosis
Other diseases that should be ruled out before a
diagnosis of EVD can be made include: malaria,
typhoid fever, shigellosis, cholera, leptospirosis,
plague, rickettsiosis, relapsing fever, meningitis,
hepatitis and other viral haemorrhagic fevers.
Ebola virus infections can be diagnosed
definitively in a laboratory through several types
of tests:
antibody-capture enzyme-linked
immunosorbent assay (ELISA)
antigen detection tests
serum neutralization test
reverse transcriptase polymerase chain
reaction (RT-PCR) assay
electron microscopy
virus isolation by cell culture.
Samples from patients are an extreme biohazard
risk; testing should be conducted under
maximum biological containment conditions.
Vaccine and treatment
No licensed vaccine for EVD is available. Several
vaccines are being tested, but none are available
for clinical use.
Severely ill patients require intensive supportive
care. Patients are frequently dehydrated and
require oral rehydration with solutions containing
electrolytes or intravenous fluids.
No specific treatment is available. New drug
therapies are being evaluated.
Natural host of Ebola virus
In Africa, fruit bats, particularly species of the
genera Hypsignathus monstrosus, Epomops
franqueti and Myonycteris torquata , are
considered possible natural hosts for Ebola virus.
As a result, the geographic distribution of
Ebolaviruses may overlap with the range of the
fruit bats.
Ebola virus in animals
Although non-human primates have been a
source of infection for humans, they are not
thought to be the reservoir but rather an
accidental host like human beings. Since 1994,
Ebola outbreaks from the EBOV and TAFV
species have been observed in chimpanzees and
gorillas.
RESTV has caused severe EVD outbreaks in
macaque monkeys (Macaca fascicularis) farmed
in Philippines and detected in monkeys imported
into the USA in 1989, 1990 and 1996, and in
monkeys imported to Italy from Philippines in
1992.
Since 2008, RESTV viruses have been detected
during several outbreaks of a deadly disease in
pigs in People’s Republic of China and
Philippines. Asymptomatic infection in pigs has
been reported and experimental inoculations
have shown that RESTV cannot cause disease in
pigs.
Prevention and control
Controlling Reston ebolavirus in domestic
animals
No animal vaccine against RESTV is available.
Routine cleaning and disinfection of pig or
monkey farms (with sodium hypochlorite or other
detergents) should be effective in inactivating the
virus.
If an outbreak is suspected, the premises should
be quarantined immediately. Culling of infected
animals, with close supervision of burial or
incineration of carcasses, may be necessary to
reduce the risk of animal-to-human
transmission. Restricting or banning the
movement of animals from infected farms to
other areas can reduce the spread of the disease.
As RESTV outbreaks in pigs and monkeys have
preceded human infections, the establishment of
an active animal health surveillance system to
detect new cases is essential in providing early
warning for veterinary and human public health
authorities.
Reducing the risk of Ebola infection in people
In the absence of effective treatment and a
human vaccine, raising awareness of the risk
factors for Ebola infection and the protective
measures individuals can take is the only way to
reduce human infection and death.
In Africa, during EVD outbreaks, educational
public health messages for risk reduction should
focus on several factors:
Reducing the risk of wildlife-to-human
transmission from contact with infected fruit
bats or monkeys/apes and the consumption
of their raw meat. Animals should be handled
with gloves and other appropriate protective
clothing. Animal products (blood and meat)
should be thoroughly cooked before
consumption.
Reducing the risk of human-to-human
transmission in the community arising from
direct or close contact with infected patients,
particularly with their bodily fluids. Close
physical contact with Ebola patients should
be avoided. Gloves and appropriate personal
protective equipment should be worn when
taking care of ill patients at home. Regular
hand washing is required after visiting
patients in hospital, as well as after taking
care of patients at home.
Communities affected by Ebola should inform
the population about the nature of the disease
and about outbreak containment measures,
including burial of the dead. People who have
died from Ebola should be promptly and
safely buried.
Pig farms in Africa can play a role in the
amplification of infection because of the presence
of fruit bats on these farms. Appropriate
biosecurity measures should be in place to limit
transmission. For RESTV, educational public
health messages should focus on reducing the
risk of pig-to-human transmission as a result of
unsafe animal husbandry and slaughtering
practices, and unsafe consumption of fresh
blood, raw milk or animal tissue. Gloves and
other appropriate protective clothing should be
worn when handling sick animals or their tissues
and when slaughtering animals. In regions where
RESTV has been reported in pigs, all animal
products (blood, meat and milk) should be
thoroughly cooked before eating.
Controlling infection in health-care settings
Human-to-human transmission of the Ebola
virus is primarily associated with direct or
indirect contact with blood and body fluids.
Transmission to health-care workers has been
reported when appropriate infection control
measures have not been observed.
It is not always possible to identify patients with
EBV early because initial symptoms may be non-
specific. For this reason, it is important that
health-care workers apply standard precautions
consistently with all patients – regardless of
their diagnosis – in all work practices at all
times. These include basic hand hygiene,
respiratory hygiene, the use of personal
protective equipment (according to the risk of
splashes or other contact with infected
materials), safe injection practices and safe
burial practices.
Health-care workers caring for patients with
suspected or confirmed Ebola virus should apply,
in addition to standard precautions, other
infection control measures to avoid any exposure
to the patient’s blood and body fluids and direct
unprotected contact with the possibly
contaminated environment. When in close
contact (within 1 metre) of patients with EBV,
health-care workers should wear face protection
(a face shield or a medical mask and goggles), a
clean, non-sterile long-sleeved gown, and gloves
(sterile gloves for some procedures).
Laboratory workers are also at risk. Samples
taken from suspected human and animal Ebola
cases for diagnosis should be handled by trained
staff and processed in suitably equipped
laboratories.
WHO response
WHO provides expertise and documentation to
support disease investigation and control.
Recommendations for infection control while
providing care to patients with suspected or
confirmed Ebola haemorrhagic fever are provided
in: Interim infection control recommendations for
care of patients with suspected or confirmed
Filovirus (Ebola, Marburg) haemorrhagic fever,
March 2008. This document is currently being
updated.
WHO has created an aide–memoire on standard
precautions in health care (currently being
updated). Standard precautions are meant to
reduce the risk of transmission of bloodborne and
other pathogens. If universally applied, the
precautions would help prevent most
transmission through exposure to blood and
body fluids.
Standard precautions are recommended in the
care and treatment of all patients regardless of
their perceived or confirmed infectious status.
They include the basic level of infection control—
hand hygiene, use of personal protective
equipment to avoid direct contact with blood and
body fluids, prevention of needle stick and
injuries from other sharp instruments, and a set
of environmental controls.
Via @FreshMindWorld
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