Essay/Term paper: The ebola virus

Essay, term paper, research paper:  Medicine

The Ebola Virus


INTRODUCTION

The most deadly killers on this earth are too small to see with the
naked eye. These microscopic predators are viruses. In my report, I will
answer many basic questions concerning one of the fastest killing viruses, the
Ebola virus. Questions such as "How does it infect its victims?", "How are
Ebola victims treated?", "How are Ebola outbreaks controlled?" and many others
related to this deadly virus.

GENERAL INFORMATION

The Ebola virus is a member of the negative stranded RNA viruses known
as filoviruses. There are four different strains of the Ebola virus - Zaire
(EBOZ), Sudan (EBOS), Tai (EBOT) and Reston (EBOR). They are very similar
except for small serological differences and gene sequence differences. The
Reston Strain is the only one which does not affect humans. The Ebola virus
was named after the Ebola river in Zaire, Africa after its first outbreak in
1976.

STRUCTURE

When magnified by an electron microscope, the ebola virus resembles long
filaments and are threadlike in shape. It usually is found in the form of a "U-
shape". There are many 7nm spikes which are 10nm apart from each other visible
on the surface of the virus. The average length and diameter of the virus is
920nm and 80nm. The virons are highly variable in length (polymorphic), some
attaining lengths as long as 14000nm. The Ebola virus consists of a helical
nucleocapsid, which is a protein coat and the nucleic acid it encloses, and a
host cell membrane, which is a lipoprotein unit that surrounds the virus and
derived form the host cell's membrane. The virus is composed of 7 polypeptides,
a nucleoprotein, a glycoprotein, a polymerase and 4 other undesignated proteins.
These proteins are synthesized by mRNA that are transcribed by the RNA of the
virus. The genome consists of a single strand of negative RNA, which is
noninfectious itself. The order of it is as follows: 3' untranslated region,
nucleoprotein, viral structured protein, VP35, VP40 glycoprotein, VP30, VP24,
polymerase(L), 5' untranslated region. HOW IT INFECTS

Once the virus enters the body, it travels through the blood stream and
is replicated in many organs. The mechanism used to penetrate the membranes of
cells and enter the cell is still unknown. Once the virus is inside a cell, the
RNA is transcribed and replicated. The RNA is transcribed, producing mRNA which
are used to produce the virus' proteins. The RNA is replicated in the cytoplasm
and is mediated by the synthesis of an antisense positive RNA strand which
serves as a template for producing additional Ebola genomes. As the infection
progresses, the cytoplasm develops "prominent inclusion bodies" which means that
it will contain the viral nucleocapsid that will become highly ordered. The
virus then assembles and buds off from the host cell, while obtaining its
lipoprotein coat from the outer membrane. This destruction of the host cell
occurs rapidly, while producing large numbers of viruses budding from it.

WHAT IT INFECTS

The Ebola virus mainly attacks cells of the lymphatic organs, liver,
kidney, ovaries, testes, and the cells of the reticuloendothelial system. The
massive destruction of the liver is the trademark of Ebola. The victim looses
vast amounts of blood especially in mucosa, abdomen, pericardium and the vagina.
Capillary leakage and bleeding leads to a massive loss in intravascular volume.
In fatal cases, shock and acute respiratory disorder can also be seen along with
the bleeding. Numerous victims are delirious due to high fevers and many die of
intractable shock. SYMPTOMS

During the onset of Ebola, the host will experience weakness, fever,
muscle pain, headache and sore throat. As the infection progresses, vomiting
(usually black), limited kidney and liver function, chest and abdominal pain,
rash and diarrhoea begin. External bleeding from skin and injection sites and
internal bleeding from organs occur due to failure of blood to clot.

TRANSMISSION

How "patient zero" (first to be infected) acquires natural infection is
still a mystery. After the first person is infected, further spread of Ebola to
other humans (secondary transmission) is due to direct contact with bodily
fluids such as blood, secretions and excretions. It is also spread through
contact with the patients skin which carries the virus. Spread can be
accomplish either by person to person transmission, needle transmission or
through sexual contact. Person to person transmission occurs when people have
direct contact with Ebola patients and do not have suitable protection. Family
members and doctors who contract the virus usually obtain it from this type of
transmission. Needle transmission occurs when needles, which have been used on
Ebola patients, are reused. This happens frequently in developing countries
such as Zaire and Sudan because the heath care is underfinanced. A lucky person
who has recovered from the Ebola virus can also infect another person though
sexual contact. This is because the person may still carry the virus in his/her
genital. A fourth method of transmission is airborne transmission. This type
is not proven 100% although there have been several experiments done to prove
that this type of transmission is highly possible. The time between the
invasion of Ebola and the appearance of its symptoms (incubation period) is 2-21
days.

HOW IT IS DIAGNOSED

Diagnosing the Ebola virus may take up to 10 days. The methods used to
detect the virus are very slow, compared to how rapid Ebola can kill its victims.
Blood or tissue samples are sent to a high- containment laboratory designed for
working with infected substances and are tested for specific antigens,
antibodies or the viruses genetic material itself. Recently, a skin test has
been developed which can detect infections much faster. A skin biopsy specimen
is fixed in a chemical called Formaline, which kills the virus, and is then
safely transported to a lab. It is processed with chemicals and if the dead
Ebola virus is present, the specimen will turn bright red.

TREATMENT

No treatment, vaccine, or antiviral therapy exists. Roughly ninety
percent of all Ebola's victims die. The patient can only receive intensive
supportive care and hope that they can be one of the fortunate ten percent who
survive.
In November of 1995, Russian scientist claimed that they had discovered
a cure for Ebola. It uses an antibody called Immunoglobulin G (IgG). They
immunized horses with it and challenged them with live Ebola Zaire viruses. The
scientists took their blood and used it as antiserum. With the antiserum, they
have developed Ebola immune sheep, goat, pigs and monkeys. USAMRIID (USA
Medical Research Institute for Infections Disease) received some equine
Immunoglobulin and had some successes but fell short of the great claims of the
Russians. This discovery does give grounds for optimism that an effective cure
for Ebola can be found.

CONTROL OF THE OUTBREAK

To control an outbreak of Ebola, you must prevent further spread of the
virus. The CDC (Center for Disease and Control) usually sends a team of medical
scientists to the area of the outbreak where they provide advice and assistance
to prevent additional cases. To limit the spread, they collect specimens, study
the course of the virus, and look for others who may have been in contact with
the virus. If anyone has been exposed to the virus, they are put under close
surveillance and are sprayed with chemicals. The patients are isolated to
interrupt person to person spread at the hospitals. This is called the "barrier
technique". 1) All hospital personnel in contact with the patient must wear
protective gear such as gowns, masks, gloves, and goggles. 2) Visitors are not
allowed. 3) Disposable materials and wastes are removed or burned after use. 4)
Reusable materials, such as syringes and needles are sterilized. 5) All surfaces
are cleaned with sanitizing solution. 6) Fatal cases are buried or cremated. The
outbreak is officially over when two maximum incubation periods (42 days) have
passed without any new cases.

PAST OUTBREAKS

In the past, there has been 4 major outbreaks. The first occurred in
1976 in Zaire, Africa where there were 280 fatalities out of 318 cases. The
second also occurred in 1976, but in a nearby country, Sudan, Africa where 150
additional victims out of 250 cases died. In total, there were 340 deaths out
of the 568 who were infected, a death rate of almost 60%. A smaller outbreak
arose in 1979, also in Sudan. There were only 34 cases and 22 fatalities. Tiny
outbreaks have occurred periodically in Africa up until 1995. In 1995, after 16
years of hiding, the fourth appearance of Ebola emerged and devastated Africa
once again. This time it was in Kikwit, Zaire. The first patient was
discovered on January the 6th and the outbreak was officially over on August the
24th (see chart for death distribution of each month during its peak - 212
deaths). There was a total of 315 cases and 244 deaths, a 77% fatality rate.

THE ANIMAL RESOVOIR

The animal species which carries the Ebola virus has not been found.
Since outbreaks begin when man comes in contact with the animal resovoir,
scientist have made several attempts during the 1970 outbreaks to find it, but
have been unsuccessful. The 1995 outbreak gave scientist a perfect opportunity
to search for the source once again. After locating "patient zero", a charcoal-
maker named Gaspard Menga, they decided to search the jungle where he probably
came in contact with Ebola. They collected over 18,000 animals and 30,000
insects. These include mosquitoes, hard ticks, rodents, birds, bats, cats,
small bush antelope, snakes, lizards and a few monkeys. After collecting, the
specimens are tested for antibodies of Ebola or Ebola itself. The scientist
will continue searching until the end of the year, hoping that they will find
the animal resovoir.