FREE ESSAY ON A VIRUS

A 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 known 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'. 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. The blood fails to clot and patients may
bleed from injections sites and into the gastrointestinal tract, skin and internal
organs. 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. 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. 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. 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%. 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. 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. 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. 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%. 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. 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. 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. 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.
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 there are no known 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 too many downfalls that
would over shadow the mass spread of the diseases. First the virus is easily destroyed by
disinfectants. 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. 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.