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Ebola Hemorrhagic Fever >
Questions and Answers about Ebola Hemorrhagic
Fever
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What
is Ebola hemorrhagic fever? |
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![Ebola virus electron micrograph](https://webarchive.library.unt.edu/eot2008/20090116085617im_/http://www.cdc.gov/ncidod/dvrd/spb/images/pathimag/ebola_em.gif) |
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Electron
micrograph of Ebola virus. |
Ebola hemorrhagic
fever (Ebola HF) is a severe, often-fatal disease in humans and nonhuman
primates (monkeys, gorillas, and chimpanzees) that has appeared sporadically
since its initial recognition in 1976.
The disease is caused
by infection with Ebola virus, named after a river in the Democratic Republic
of the Congo (formerly Zaire) in Africa, where it was first recognized.
The virus is one of two members of a family of RNA viruses called the
Filoviridae. There are five identified subtypes of Ebola virus. Four of the five have caused disease in humans: Ebola-Zaire, Ebola-Sudan,
Ebola-Ivory Coast and Ebola-Bundibugyo. The fifth, Ebola-Reston, has caused disease in nonhuman
primates, but not in humans.
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Where
is Ebola virus found in nature? |
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The exact origin,
locations, and natural habitat (known as the "natural reservoir")
of Ebola virus remain unknown. However, on the basis of available evidence
and the nature of similar viruses, researchers believe that the virus
is zoonotic (animal-borne), with 4 of the 5 subtypes occurring in an animal host
native to Africa. A similar host, most likely in the Philippines, is probably associated
with the Ebola-Reston subtype, which was isolated from infected cynomolgous monkeys
that were imported to the United States and Italy from the Philippines.
The virus is not known to be native to other continents, such as North
America.
Where
do cases of Ebola hemorrhagic fever occur? |
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Confirmed cases of
Ebola HF have been reported in the Democratic Republic of the Congo, Gabon,
Sudan, the Ivory Coast, Uganda, and the Republic of the Congo. No case of the disease in humans
has ever been reported in the United States. Ebola-Reston virus caused
severe illness and death in monkeys imported to research facilities in
the United States and Italy from the Philippines; during these outbreaks,
several research workers became infected with the virus, but did not become
ill.
Ebola HF typically appears in sporadic outbreaks,
usually spread within a health-care setting (a situation known as amplification).
It is likely that sporadic, isolated cases occur as well, but go unrecognized.
A table showing a chronological list of known
cases and outbreaks is available.
How
is Ebola virus spread? |
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Infections with Ebola
virus are acute. There is no carrier state. Because the natural reservoir
of the virus is unknown, the manner in which the virus first appears in
a human at the start of an outbreak has not been determined. However, researchers
have hypothesized that the first patient becomes infected through contact
with an infected animal.
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![Treating Ebola HF patients](https://webarchive.library.unt.edu/eot2008/20090116085617im_/http://www.cdc.gov/ncidod/dvrd/spb/images/ebohosp.jpg) |
Treating
patients with Ebola HF during outbreak of the disease in Kikwit, Democratic
Republic of the Congo, in 1995. |
After the first case-patient
in an outbreak setting is infected, the virus can be transmitted in several
ways. People can be exposed to Ebola virus from direct contact with the
blood and/or secretions of an infected person. Thus, the virus is often
spread through families and friends because they come in close contact
with such secretions when caring for infected persons. People can also
be exposed to Ebola virus through contact with objects, such as needles,
that have been contaminated with infected secretions.
Nosocomial transmission
refers to the spread of a disease within a health-care setting, such as
a clinic or hospital. It occurs frequently during Ebola HF outbreaks.
It includes both types of transmission described above. In African health-care
facilities, patients are often cared for without the use of a mask, gown,
or gloves. Exposure to the virus has occurred when health care workers
treated individuals with Ebola HF without wearing these types of protective
clothing. In addition, when needles or syringes are used, they may not
be of the disposable type, or may not have been sterilized, but only rinsed
before reinsertion into multi-use vials of medicine. If needles or syringes
become contaminated with virus and are then reused, numerous people can
become infected.
What
are the symptoms of Ebola hemorrhagic fever? |
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The
incubation period for Ebola HF ranges from 2 to 21 days.
The onset of illness is
abrupt and is characterized
by fever, headache, joint and muscle aches, sore
throat, and weakness,
followed by diarrhea, vomiting, and stomach pain. A rash, red eyes, hiccups
and internal and external bleeding may be seen in some patients.
Researchers do not
understand why some people are able to recover from Ebola HF and others
are not. However, it is known that patients who die usually have not developed
a significant immune response to the virus at the time of death.
How
is Ebola hemorrhagic fever clinically diagnosed? |
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Diagnosing Ebola
HF in an individual who has been infected only a few days is difficult
because early symptoms, such as red eyes and a skin rash, are nonspecific
to the virus and are seen in other patients with diseases that occur much
more frequently. However, if a person has the constellation of symptoms
described above, and infection with Ebola virus is suspected, isolate
the patient and notify local and state health departments and the CDC.
What
laboratory tests are used to diagnose Ebola hemorrhagic fever? |
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Antigen-capture enzyme-linked
immunosorbent assay (ELISA) testing, IgM ELISA, polymerase chain reaction
(PCR), and virus isolation can be used to diagnose a case of Ebola HF
within a few days of the onset of symptoms. Persons tested later in the
course of the disease or after recovery can be tested for IgM and IgG
antibodies; the disease can also be diagnosed retrospectively in deceased
patients by using immunohistochemistry testing, virus isolation, or PCR.
How
is Ebola hemorrhagic fever treated? |
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There is no standard
treatment for Ebola HF. Patients receive supportive therapy. This consists
of balancing the patients fluids and electrolytes, maintaining their
oxygen status and blood pressure, and treating them for any complicating
infections.
How
is Ebola hemorrhagic fever prevented? |
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![Ebola HF prevention poster, Kikwit, Zaire outbreak](https://webarchive.library.unt.edu/eot2008/20090116085617im_/http://www.cdc.gov/ncidod/dvrd/spb/images/ebola/ebopsterjpg.jpg) |
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Ebola
HF prevention poster used in Kikwit outbreak. |
The prevention of
Ebola HF in Africa presents many challenges. Because the identity and
location of the natural reservoir of Ebola virus are unknown, there are
few established primary prevention measures.
If cases of the disease
do appear, current social and economic conditions often favor the spread
of an epidemic within health-care facilities. Therefore, health-care providers
must be able to recognize a case of Ebola HF should one appear. They must
also have the capability to perform diagnostic tests and be ready to employ
practical viral hemorrhagic fever isolation precautions, or barrier nursing
techniques. These techniques include the wearing of protective clothing,
such as masks, gloves, gowns, and goggles; the use of infection-control
measures, including complete equipment sterilization; and the isolation
of Ebola HF patients from contact with unprotected persons. The aim of
all of these techniques is to avoid any persons contact with the
blood or secretions of any patient. If a patient with Ebola HF dies, it
is equally important that direct contact with the body of the deceased
patient be prevented.
CDC has developed
a set of tools to meet health-care facilities' needs. In conjunction with
the World Health Organization, CDC has developed practical, hospital-based
guidelines, entitled Infection Control for
Viral Haemorrhagic Fevers In the African Health Care Setting. The
manual describes how to recognize cases of viral hemorrhagic fever, such
as Ebola HF, and prevent further nosocomial transmission by using locally
available materials and few financial resources. Similarly, a practical
diagnostic test that uses tiny samples from patients skin has been
developed to retrospectively diagnose Ebola HF in suspected case-patients
who have died.
What
challenges remain for the control and prevention of Ebola hemorrhagic
fever? |
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Scientists and researchers
are faced with the challenges of developing additional diagnostic tools
to assist in early diagnosis of Ebola HF and conducting ecological investigations
of Ebola virus and its possible reservoir. In addition, one of the research
goals is to monitor suspected areas to determine the incidence of the
disease. More extensive knowledge of the natural reservoir of Ebola virus
and how the virus is spread must be acquired to prevent future outbreaks
effectively.
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