Ebola Virus Essay, Research Paper
The Ebola Virus
A virus is an ultramicroscopic infectious organism that, having no independent
metabolic activity, can replicate only within a cell of another host organism. A virus
consists of a core of nucleic acid, either RNA or DNA, surrounded by a coating of
antigenic protein and sometimes a lipid layer surrounds it as well. The virus provides the
genetic code for replication, and the host cell provides the necessary energy and raw
materials. There are more than 200 viruses that are know to cause disease in humans. The
Ebola virus, which dates back to 1976, has four strains each from a different geographic
area, but all give their victims the same painful, often lethal symptoms.
The Ebola virus is a member of a family of RNA viruses known as ‘Filoviriade’
and falling under one genus, ‘Filovirus’. “The Ebola virus and Marburg virus are the two
known members of the Filovirus family” (Journal of the American Medical Association
273: 1748). Marburg is a relative of the Ebola virus. The four strains of Ebola are Ebola
Zaire, Ebola Sudan, Ebola Reston, and Ebola Tai. Each is named after the geographical
location in which it was discovered. These filoviruses cause hemorrhagic fever, which is
actually what kill victims of the Ebola virus. Hemorrhagic fever as defined in Mosby’s
Medical, Nursing, and Allied Health Dictionary as, a group of viral aerosol infections,
characterized by fever, chills, headache, malaise, and respiratory or GI symptoms,
followed by capillary hemorrhages, and, in severe infection, oliguria, kidney failure,
hypotension, and, possibly, death. The incubation period for Ebola Hemorrhagic Fever
ranges from 2-21 days (JAMA 273: 1748). The blood fails to clot and patients may bleed
from injections sites and into the gastrointestinal tract, skin and internal organs (Ebola
Info. from the CDC 2). The Ebola virus has a tropism for liver cells and macrophages,
macrophages are cells that engulf bacteria and help the body defend against disease.
Massive destruction of the liver is a hallmark feature of Ebola virus infection. This virus
does in ten days what it takes AIDS ten years to do. It also requires biosaftey level four
containment, the highest and most dangerous level. HIV the virus that causes AIDS
requires only a biosaftey level of two. In reported outbreaks, 50%-90% of cases have
been fatal (JAMA 273: 1748).
Ebola can be spread in a number of ways, and replication of the virus occurs at an
alarming rate. Ebola replication in infected cells takes about eight hours. Hundreds to
thousands of new virus particles are then released during periods of a few hours to a few
days, before the cells die. The several cycles of replication occur in a primate before the
onset of the fever and other clinical manifestations (Ornstein, Matthews and Johnson 7).
In most outbreaks, transmission from patient to patient within hospitals has been
associated within the reuse of unsterile needles and syringes. High rates of transmission
in outbreaks have occurred from patients to heath-care workers and to family members
who provide nursing care without appropriate precautions to prevent exposure to blood,
other body fluids, vomitus, urine and stool. Risk for transmitting the infection appears to
be highest during the later stages of illness, which are often characterized by vomiting,
diarrhea, shock, and frequently hemorrhaging (JAMA 274: 374). Even a person who has
recovered from the symptoms of the illness may have the virus present in the genital
secretions for a brief period after. This makes it possible for the virus to be spread by
sexual contact. Complete recovery is reached only when no particles of the virus are left
in the body fluids, this however is rarely attained. The disease, for humans, is not
airborne, capable to be passed on through air travel, but for nonhuman primates it has
been a possibility in a few cases.
Ebola Zaire was identified in 1976 in Northern Zaire and was the first
documented appearance of the virus. This strain of the virus effects humans and
nonhuman primates. Close contact and dirty needles spread the Ebola virus. The center
of the epidemic in Zaire involved a missionary hospital where they reused needles and
syringes without sterilization. Most of the staff of the hospital got sick and died. This
outbreak infected 318 with a death rate of 93% (Le Guenno et al. 1271). Another fatal
case was reported one year later in Zaire but nothing major ever became of it. The most
recent case recorded was the infamous breakout in Kikwit, Zaire. This breakout had the
world in an uproar about the possibility of this virus spreading out globally. This
outbreak appeared to have started with a patient who had surgery in Kikwit on April 10,
1995. Members of the surgical team then developed symptoms similar to those of a viral
hemorrhagic fever disease (Ebola Info. from the CDC 2). From there, the disease spread
to more than 300 others. The most frequent symptoms at the onset were fever (94%),
diarrhea (80%), and server weakness (74%); other symptoms included dysphagia (41%)
and hiccups (15%). Clinical signs of bleeding occurred in 38% of cases (JAMA 274:
373). The World Heath Organization declared on August 24, 1995 that the outbreak of
Ebola Zaire in Kikwit was officially over after killing 244 of its 315 known victims
(”Ebola Outbreak Officially Over” 1). This outbreak had a rate of death over 75%.
Ebola Sudan also occurred in 1976 about the same time as Ebola Zaire. The
number of cases was 284 with a death rate of 53% (Le Guenno et al 1271). The outbreak
occurred in a hospital setting. In 1979 a small epidemic was acknowledged in the same
town of Sudan. Of the thirty-four recorded cases there were twenty-two fatalities (Ebola
Info. from the CDC 1). Again the setting for the small epidemic was a hospital setting
with inadequate supplies and unsanitary conditions.
Ebola Reston was isolated in 1989 during an outbreak of cynomolgus monkeys in
a quarantine in Reston, Virginia (Le Guenno et al 1271). These monkeys were imported
to the U.S. from the Philippines. This was the only outbreak of the virus to go outside the
continent of Africa. This Reston strain of Ebola appears to be highly pathogenic for some
monkey species but not for man (Le Guenno et al 1271). No humans fell victim or even
contracted the virus. This also is the only known strain to be able to be transferred
through the air.
Ebola Tai, which was named after the forest in which it was found, is the newest stain of
the Ebola family. A Swiss female zoologist, who performed an autopsy on a chimpanzee
infected with the same virus in the wild, contracted it. This occurred in the Ivory Coast,
West Africa in mid November of 1994. This is the only know case of Ebola Tai and is
the first recorded case that infection of a human has been linked to naturally infected
monkeys anywhere on the African continent. It is also not clear how the chimpanzee may
have contracted the disease.
The usual hosts for these types of hemorrhagic causing viruses are rodents, ticks or
mosquitos. The natural reservoir for Ebola viruses has not been identified and … because
of the high mortality rate seen in apes they are unlikely to be the reservoir (Le Guenno et
al 1271). Thousands of animals captured near outbreak areas, are tested for the virus, but
efforts have always been unsuccessful.
The Ebola might never pose a problem to the world community but, the virus itself is
armed with several advantages. It has the ability to mutate into new strains as we have
seen over time. The fact that there are no know hosts, which means that there is no way
to create a vaccine, coupled with the fact that poor sanitary conditions and lack of
medical supplies worsen the spreading of the disease, meaning that there could be a
slight chance that the virus could probably become an international problem.
Even if an international crisis were to occur, the virus has to many downfalls that would
over shadow the mass spread of the diseases. First the virus is easily destroyed by
disinfectants (Ebola Info. from the CDC 3). Also, under ultraviolet light the virus falls
apart. This ultraviolet light smashes their genetic material making them unable to
replicate. Ebola’s virulence may also serve to limit its speed: its victims die so quickly
that they do not have a chance to spread the infection very far. In order for the virus to
become airborne it would have to mutate in such a way that its outer protective coating of
proteins, the capsid, could resist the forces to which they are subjected in air, like dryness
and heat. It would also probably need to change structure to allow infection through the
respiratory system. There are no exact measures of the rate of Ebola mutation, but the
probability of the required mutations happening is very low (Ornstein, Matthews and
Johnson 4).
There is no cure or vaccine and it is still unclear if blood from survivors that contain
antibodies can be used to synthesize a serum to treat the disease with. Some patients have
had symptoms subside with the transfusion of survivors blood but not connection to the
antibodies and the relief of the illness was proven. There is a good chance that a vaccine
may never be synthesized. The kind of research needed to develop a modified live virus
vaccine simply could not be done, given the scope of the problem. That is, only a few
people would be working in labs who would need to be vaccinated, and a vaccine might
want to stockpile in the event of an epidemic. Nevertheless, these are not the scale of
circumstances under which the development of a vaccine could be afforded (Dr. F.A.
Murphy 3).