FREE ESSAY ON THE EBOLA VIRUS

THE EBOLA VIRUS

Ebola Hemorrhagic Fever
In the world today, there are many known deadly viruses, but few present as great a
threat as Ebola, the virus that causes Ebola Hemorrhagic Fever. Key factors in
understanding Ebola HF include: Its history, plan of attack, and the diagnosis and
treatment of the disease.
The Ebola virus can, and usually does cause a disease called Ebola hemorrhagic fever,
which is a Viral hemorrhagic fever. According to the proceedings of the 4th National
Symposium on Biosafety, the clinical definition for Viral hemorrhagic fever is as
follows. Viral hemorrhagic fever is an acute infection that begins with fever, myalgia,
malaise and progresses to prostration. It shows evidence of vascular dysregulation and
increased vascular permeability and can include multisystem involvement. The hemorrhage
indicates extent of small vessel involvement but not necessarily large in volume. Shock,
encephalopathy, extensive hemorrhage, and poor prognosis should be expected (4th National
2). The Ebola virus is named after a river in the Democratic Republic of the Congo
(formerly Zaire) in Africa, where it was first recognized. The Ebola virus is closely
related to the Marburg virus. Both are members of a relatively new family of viruses
called Filoviradae. Ebola hemorrhagic fever is classified as a BSL-4 (biosafety level 4)
agent, which is the most dangerous in the Centers for Disease Control and Prevention
(CDC) classification system. BSL-4 agents are exotic agents that pose a high risk of
life-threatening disease, and for which there is no vaccine or therapy. Ebola hemorrhagic
fever is a severe, often-fatal disease in humans and non human primates (monkeys and
chimpanzees) that has appeared sporadically since its initial recognition in 1976 (CDC
1).
Common human perceptions of this virus are, for the most part, accurate in that it is a
highly contagious agent that can cause a fatal disease called Ebola hemorrhagic fever.
Although, there are a few misconceptions such as the belief that the virus can be
transmitted from person to person through the air, which is not known to be true, and
later explained. Also, contrary to popular assumptions, humans are not carriers of the
virus, as we are with the influenza virus, 
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for example. The initial patient in an outbreak must have somehow contracted the virus
from an infected primate carrier, such as a monkey, which will also be explained. 
Listed, are some of the more pertinent outbreaks of Ebola hemorrhagic fever. In 1976, the
first and largest outbreak of the virus occurred in Yambuku, Zaire, killing 88% of 318
infected patients. This species was named respectively, Ebola-Zaire, and has appeared in
four other outbreaks to date. The Ebola-Sudan species appeared, naturally in the cities
of Nzara and Maridi, Sudan also in 1976. The death toll was much less than the Zaire
outbreak at 53% of 284 infected persons. In 1995, the Ebola-Zaire species struck again,
killing 81% of 315 reported cases. This time, the outbreak occurred in Kikwit, Democratic
Republic of the Congo, which was the new name Zaire.
In the United States, to date, no case of the disease in humans has ever been reported,
not to say the virus has never been here. In 1989, 1990, and 1996, Ebola, or at least a
weaker species of the virus was brought into quarantined facilities in Virginia, Texas,
and Pennsylvania by infected monkeys imported from the Philippines. In both 1989 and
1990, four humans were infected with the virus, but did not become ill. Obviously, the
species of the virus, now called Ebola-Reston, that entered the United States was a much
weaker species than those in Zaire and Sudan. The Reston outbreak served as an important
wake-up call for the U.S. Army and CDC research groups. Among other things, it
demonstrated the need for better diagnostic tools (4th National 10). 
Transmission of the Ebola virus is highly dependent upon the initial infection of a
human. It is hypothesized that the first infected human in an outbreak must have been
infected by an animal. This first infected patient in an outbreak is called the index
case. At this point, humans can transmit the virus from person to person in several ways.
People can contract the Ebola virus through contact with the blood and/or secretions of
an infected person. For this reason, this virus is commonly spread among family members
in the course of feeding, holding, or otherwise caring for infected persons in any way
that they would come in contact with such 
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secretions. Also, people can be exposed to the virus through contact with objects, such
as needles, that have been contaminated with infected secretions. 
The most common means of transmission of the Ebola virus is the spreading of the virus
throughout a health-care setting, such as a clinic or hospital, this situation is known
as amplification. In African hospitals, for example, where funds and supplies are scarce,
patients are often cared for without the use of necessary protective equipment, such as
masks, gowns, and gloves. Many cases of exposure to the virus has occurred when health
care workers have treated infected persons without using this essential clothing. In
addition, many of the needles used for injections to the ill were not of the disposable
type. When health care workers used the needles in multiple vials and on multiple
patients, they may not have been sterilized, but merely rinsed before reinsertion. If
needles or syringes become contaminated with the virus and are then reused, numbers of
people can become infected. 
The Ebola-Reston Virus species , that appeared in a primate research facility in
Virginia, may have been transmitted from monkey to monkey through the air in the facility
(CDC 2). The Ebola virus has displayed the ability to be spread through airborne
particles (aerosols) under research conditions, but this type of transmission has not
been documented among humans in a real-world setting, such as a household or hospital.
The Ebola virus appears to have an incubation period of four to sixteen days, after which
time the impact is devastating (Carson 1). One of the few things known about Ebola was
that during the initial stages of infection, the virus floods the bloodstream with a
glycoprotein--a protein with sugars attached (Glausiusz 1). This stage apparently occurs
during the incubation period. Researchers have recently learned that the glycoprotein is
part of a two-pronged attack that leaves the victim bleeding and defenseless. There are
actually two forms of the glycoprotein. The first, is released into the bloodstream, and
the second, a much larger version, stays attached to the virus. The free form has been
found to attach itself to a type of white blood cell called a neutrophil. The neutrophils
are the immune system's front line troops. 
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They attack and destroy invading viruses and signal the other fighters for the immune
system, such as the B cells that make antibodies, and the T cells that kill
virus-infected cells. Experts suspect that by binding to the neutrophils, the
glycoprotein cripples them so they cannot attack or signal other cells. This process
opens the gateway for Ebola to attack the human body.
The virus now begins its assault on the body. It attacks the body's blood vessels, using
the attached, larger glycoprotein as a key to enter endothelial cells, the cells that
line the interiors of our veins and arteries. Ebola invades and sabotages the cells'
genetic machinery in order to reproduce itself, it also damages endothelial cells, making
blood vessels leaky and weak. The patient first bleeds and then goes into shock as
falling blood pressure leaves the circulatory system unable to pump blood to vital
organs. Long before the immune system can build up enough antibodies to retaliate, a
process that can take weeks, most Ebola HF victims bleed to death.
The signs and symptoms of Ebola hemorrhagic fever are not the same for all patients, but
some of the more common early and late symptoms are listed. Within a few days after the
end of the incubation period, most Ebola patients experience: high fever, headache,
muscle aches, stomach pain, fatigue and diarrhea. Some early Ebola patients have: sore
throat, hiccups, rash, red and itchy eyes, bloody vomiting, and bloody diarrhea.
Within one week after the end of the virus's incubation period, most patients encounter:
chest pain, shock and finally death. Also, some late Ebola patients experience complete
blindness, internal hemorrhaging, hemorrhaging through the skin, and bleeding from the
ears, nose and mouth.
Diagnosing Ebola hemorrhagic fever in a person 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 patient has a combination of the symptoms described above, and
Ebola virus is suspected, several laboratory test should be performed promptly. These
include a blood film examination, 
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a blood culture, and if the patient has bloody diarrhea, a stool culture should also be
performed.
Some of the more common and accurate diagnostic tools for the detection of the Ebola
virus are the ELISA (enzyme-linked-immunosorbent serologic assay), PCR (polymerase chain
reaction, and a virus isolation procedure can be used to diagnose a case of Ebola
hemorrhagic fever within a few days of the onset of symptoms. 
Currently, there is no standard treatment for Ebola hemorrhagic fever, although most
patiens receive supportive therapy. This consists of balancing the patient's fluids and
electrolytes, maintaining their oxygen levels and blood pressure, and treating them for
any complicating infections. It is now known that The viruses [Ebola and Marburg] can be
inactivated by heating at 60?C for 1 hour, by acid treatment at pH 4 or lower, and by
organic solvents such as ether (Johnson 1). 
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 in order to determine the incidence of the disease.
More extensive knowledge of the nature of the virus' reservoir and how it is spread must
be acquired to prevent future outbreaks effectively (CDC 3). Filoviruses continue to
provide a difficult area for virologists to develop strategies to protect the public and
can be seen as the prototype of emerging viruses. We do not understand their natural
maintenance strategy and thus cannot predict their emergence nor the factors that might
reasonably be expected to increase the risk of their presenting problems to the world.
Given our profound ignorance of these viruses, the limited number of episodes we have
studied, and their lethal potential, it seems a safe bet that we have additional
unpleasant surprises in store. The task now is to gamer [sic] continuing support to
understand these elusive agents now that the epidemic has been controlled and public
interest has faded (Peters 3).
McKinney 6
Works Cited
Biosafety and Emerging Infections: Key Issues in the Prevention and Control of Viral
Hemorrhagic Fevers. Proc. of the 4th National Symposium on Biosafety. Atlanta: Centers
for Disease Control and Prevention, 1997.
Carson, Cully C., and Tracy Irons-Georges Ebola Virus. Magill's Medical Guide. 1 (1998):
511-512.
Centers for Disease Control and Prevention. Ebola Hemorrhagic Fever. Disease
Information:Viral Hemorrhagic Fevers: Fact Sheets. Atlanta: CDC, 1999.
Glausiusz, Josie. Ebola's Lethal Secrets. Discover Jul. 1998: 24.
Johnson, Karl M. Filoviradae: Ebola and Marburg Viruses. Principles and Practice of
Infectious Diseases (1989): 1303-1305.
Peters, C.J. Emerging Infections: Ebola and other Filoviruses (Emerging and Reemerging
Global Microbial Threats). The Western Journal of Medicine 164 (1996): 36-39.