What Is Ebola Hemorrhagic Fever Essay, Research Paper
What is Ebola hemorrhagic fever?
Ebola hemorrhagic fever (Ebola HF) is a severe, often-fatal disease in humans
and nonhuman primates (monkeys 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. Three of the four subtypes of Ebola virus identified
so far have caused disease in humans: Ebola-Zaire, Ebola-Sudan, and
Ebola-Ivory Coast. The fourth, Ebola-Reston, has caused disease in nonhuman
primates, but not in humans.
Where is Ebola virus found in nature?
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) and is normally maintained in an animal host
that is native to the African continent. A similar host is probably
associated with the Ebola-Reston virus subtype 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?
Confirmed cases of Ebola HF have been reported in the Democratic Republic of
the Congo, Gabon, Sudan, and the Ivory Coast. An individual with
serologic evidence of infection but showing no apparent illness has been
reported in Liberia, and a laboratory worker in England became ill as a result
of an accidental needle-stick. 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.
How is Ebola virus spread?
Infection with Ebola virus in humans is incidental — humans do not “carry”
the virus. 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. After the first case-patient in an outbreak
setting (often called the index case) 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. This is why the virus has often been spread through the families and friends of infected persons: in the course of
feeding, holding, or otherwise caring for them, family members and friends would come into close contact with such secretions. People can also be exposed to Ebola virus through contact with objects, such as needles, that have been contaminated with infected secretions. Nosocomial transmission frequently has been associated with outbreaks of Ebola HF. Nosocomial spread includes both types of transmission described
above, but the term is used to describe the spread of disease in a health-care setting such as a clinic or hospital. In African health-care facilities, patients are often cared for without the use of a mask, gown, or
gloves, and 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 re-insertion into multi-use vials of medicine. If needles or syringes become contaminated with virus and are then reused, numbers of people can become infected. The Ebola-Reston virus subtype, which was first recognized in a primate research facility in Virginia, may have been transmitted from monkey to monkey through the air in the facility. While all Ebola virus subtypes have displayed the ability to be spread through airborne particles (aerosols) under research conditions, this type of spread has not been documented among humans in a real-world setting, such as a hospital or household.
What are the symptoms of Ebola hemorrhagic fever?
The signs and symptoms of Ebola HF are not the same for all patients. The
table below outlines symptoms of the disease, according to the frequency with
which they have been reported in known cases.
Time Frame Symptoms that occur in most Ebola patients Symptoms that
in some Ebola patients
Within a few days of becoming infected with the virus: high fever, headache,
muscle aches, stomach pain, fatigue, diarrhea sore throat, hiccups, rash,
red and itchy eyes, vomiting blood, bloody diarrhea
Within one week of becoming infected with the virus: chest pain, shock,
and death blindness, bleeding
Researchers do not understand why some people are able to recover from
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
How is Ebola hemorrhagic fever clinically diagnosed?
Diagnosing Ebola HF in an individual who has been infected only a few days is
difficult because early symptoms, such as red and itchy eyes and a skin rash,
are nonspecific to the virus and are seen in other patients with diseases
that occur much more frequently. If a person has the constellation of
symptoms described in the table above, and infection with Ebola virus is
suspected, several laboratory tests should be done promptly. These include a
blood film examination for malaria and a blood culture. If the suspected
patient has bloody diarrhea, a stool culture should also be performed.
What laboratory tests are used to diagnose Ebola hemorrhagic fever?
Antigen-capture enzyme-linked immunosorbent assay (ELISA) testing, IgG
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
How is Ebola hemorrhagic fever treated?
There is no standard treatment for Ebola HF. Currently, patients receive
supportive therapy. This consists of balancing the patient’s fluids and
electrolytes, maintaining their oxygen status and blood pressure, and
treating them for any complicating infections. During a large outbreak of
Ebola HF in Kikwit, Democratic Republic of the Congo, in 1995, eight patients
were given blood of individuals who had been infected with Ebola virus but
who had recovered. Seven of the eight patient survived. However, because the
study size was small, and because the characteristics of the participants
predisposed them towards recovery, the efficacy of the treatment remains
How is Ebola hemorrhagic fever prevented?
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
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 person’s 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
Image: Ebola HF prevention poster used in Kikwit outbreak.
In conjunction with the World Health Organization, CDC has developed
practical, hospital-based guidelines, titled Infection Control for Viral
Haemorrhagic Fevers In the African Health Care Setting. The manual
describes how health care facilities can recognize cases of viral hemorrhagic
fever, such as Ebola HF, and prevent further hospital-based disease
transmission by using locally available materials and few financial resources
if a case of VHF is diagnosed in the facility. A similarly practical
diagnostic test that uses tiny samples from patients’ skin has been
to retrospectively diagnose Ebola HF in suspected case-patients who have died.
What challenges remain for the control and prevention of Ebola
Scientists and researchers are faced with the challenges of developing
additional diagnostic tools to assist in early diagnosis of the disease and
ecological investigations of Ebola virus and the disease it causes. 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.
Center For Disease Control Center
World Book 2000