What Is Ebola Hemorrhagic Fever Essay Research

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

be prevented.

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


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