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Ebola Virus Essay, Research Paper

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, 2 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 3 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. 4 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, 5 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).

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.


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