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, nucleoprote
in, 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. Th
is 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.
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