Ebola Virus Replication In Infected Body Cells example essay topic

The female scientist, fully dressed in a quarantine outfit, anxiously prepared to inject a sedative into the arm of the delirious patient. Although he was being held down by several pairs of arms, he was still putting up a good fight. The needle goes in. He jerks. The needle flicks into the forefinger of the scientist. The scientist stares at her finger in shock and disbelief, and runs away.

It would only be a few days now before she would die. Thankfully, this is only a scene out of the 1995 box-office hit, Outbreak (Fig. 3), which was about Americans fighting against the spread of a nationwide epidemic caused by one of the most feared viruses of our time: the Ebola virus. I chose this topic out of curiosity; everyone shudders at the mention of this virus, and I have always wondered why people do so. This project will give me the opportunity to further investigate what are the factors which make the Ebola virus so deadly and so feared by man.

What exactly is Ebola Ebola is a viral hemorrhagic fever actually named after the River Ebola in Zaire, Africa, where it was first discovered. It belongs to a genus of ribonucleic viruses called filoviruses, under the family Filofiridae, which are characterized by their filament-like (thread-like) appearance with a little hook or loop at the end. Only five viruses exist in this family: the not-as-deadly Marburg, and the four Ebola strains: Ebola Zaire, Ebola Sudan, Ebola Tai and Ebola Reston. The latter only affects monkeys and hence is not harmful to man. (Ebola-Reston-infected monkeys display symptoms similar to the symptoms of the Ebola- Zaire virus shown in humans.) The first emergence of Ebola into the modern world took place in 1976, its 'grand entrance' in the form of two major outbreaks which happened almost simultaneously in Zaire (Fig. 2) and western Sudan, Africa.

The mortality rate was 88% in Zaire and 53% in Sudan. Mor than 550 cases were reported and more than 340 died. The third outbreak took place in Sudan in the same area as before, resulting in 34 cases and 22 deaths. More recently, outbreaks have occurred in Kik wit, Zaire in 1994, and Gabon in 1994 and 1996.

The most recent outbreak may have possibly taken place in Congo in early 1999; a virus similar to Ebola killed 63 people. There has only been one recorded case of Ebola Tai infection: in 1994, a Swiss researcher caught the virus after conducting an autopsy on a chimpanzee in the Tai Forest, Ivory Coast. She was given intensive treatment in Switzerland, and survived. In total, there have been 1100 cases and 793 deaths officially resulting in Ebola since its discovery.

(Tables I and II) The viruses in this family range from 800 to 1000 nanometers in length. Marburg and Ebola are distinguished by their length after purification. Infectivity depends on particular lengths: the longer, the more infectious. All Ebola viruses measure up to about the same length. Each virus particle consists of a helical-coiled tube made of four virally encoded proteins. This strand of RNA is found in an envelope formed from the host's plasma cell membrane, which is now spiked with another carbohydrate-coated viral protein.

Differences in gene sequence and very small differences in serological nature are what make each Ebola virus unique from each other, with its own antigenic and biological properties. The time needed for Ebola virus replication in infected body cells takes less than eight hours. Hundreds to thousands of new viral particles can be produced and released from the host cell within days or even hours before the host cell dies. This replication process is repeated several times in an Ebola patient before symptoms begin to show. The diagnosis of Ebola is made by the detection of Ebola antibodies, antigens or genetic material, or by the culture of the virus, in blood or other bodily fluid specimens that are examined in specialized laboratory tests.

Such tests present a very extreme biohazard, so they are conducted in special high-containment laboratories to ensure maximum protection for scientists. The Center of Disease Control and Prevention (CDC) has classified the Ebola virus under Biosafety Level 4, which requires the greatest safety precautions. The technique used to diagnose the virus is called ELISA (Enzyme- Linked Immunosorbent Assay) that searches for specific antigens and antibodies found in the patient's blood. A technique called the polymerase chain reaction is used to duplicate genetic material for analysis of patient tissue or blood for viral detection purposes. The symptoms of Ebola make it one of the most gruesome and horrifying ways to die: victims ultimately die because the virus liquefies their insides. Like all forms of viral hemorrhagic fevers, Ebola symptoms start off as fever and muscle aches four to sixteen days after infection.

Other minor health problems such as loss of appetite, weakness, conjunctivitis, and sore throat can also occur. Depending on the specific virus, the patient can then become extremely ill with respiratory problems, diarrhoea, rash, vomiting, severe kidney and liver problems, and shock. Internal and external bleeding results because blood fails to clog. Patients may bleed from injection sites as well as into the gastrointestinal tract, skin, and internal organs.

Patients are prone to mental agitation, confusion and delirium. The Ebola's rapid attack on the human body will now we investigated on a micro level. There is a myth about the virus being able to infect just about any kind of cell. In actual fact, the Ebola virus specifically attacks the liver cells and cells of the reticuloendothelial system. The lining of capillaries are attacked, and they start to leak fluids and plasma proteins.

Sometimes poor clotting capability results from intravascular coagulation. In due time, this will lead to shock due to low water volume in the body (hypovolemia). This consequently causes critical organ failure due to interruption of tissue oxygenation. At the usually irreversible stage of critical shock, the chances of living are almost nil.

Ebola epidemics arise because the virus is highly contagious. Transmission is most common through close personal contact with one that has contracted the illness. This is because the virus is carried in the victim's bodily fluids, including blood, secretions and even semen. This means that transmission is also possible through sexual contact. The first outbreaks in Zaire and Sudan arose mainly due to the fact that hypodermic needles used to treat infected patients were reused and not sterilized in the hospitals. (The reuse of needles and syringes there is a common practice because the under financed medical system.) Transmission is also possible by dealing with infected primates, as demonstrated in the case of the Swiss zoologist who contracted the Ebola-Tai virus after performing an autopsy on an infected chimpanzee in 1994.

Transmission to another person can occur even before the patient himself has yet to show Ebola symptoms. If a patient does recover, her or his chances of spreading the virus is greatly reduced, but there are still possible chances of transmission through sexual contact, as the virus may still be present in genital secretions up to a period of seven weeks after recovery. The chances of transmission are therefore zero only after the patient has completely recovered and there are no traces of the virus whatsoever in the patient. However, if a patient dies, the body remains infectious, and therefore must be handled with extreme caution.

Ebola cannot recur in a survivor; a fully recovered survivor has no traces of the virus in his or her system. The only way a survivor will catch the illness again is by re-infection. Thankfully, the Ebola virus is not an airborne disease. Ebola- Reston is the only strain that could possibly be transmitted between monkeys through the air.

At the moment, there is no present form of antiviral treatment for Ebola patient, and interferon is not able to affect the virus in any way. While intensive research is still in progress to find an appropriate form of treatment, intensive supportive care can only be given to patients, who are in a constant state of dehydration and recurrently need intravenous fluids. The handling of fluids and electrolytes is done with extreme caution. Replacement of plasma albumin is helpful prior to the stage of clinical shock. There is no cure for the Ebola virus, nor is there a vaccine for protection against it. Vaccines must be specific to certain strains.

Therefore, a universal vaccine for all four Ebola strains is not likely to be produced. There are many factors that could lead to an Ebola epidemic. Here is a list of conditions that could contribute to such a disastrous event. - the presence of animal or insect vectors near a human population; - exposure of the virus to an individual in a remote setting, and the individual returning to a more highly populated area; - poor hygiene and sanitation in a human population, hence increasing the chances of contact with bodily fluid (e.g. excretion from Ebola patients get into sewage system and human contact is common); - decreased immunity level in population; - insufficient public health infrastructure (e.g. hospital facilities); - lack of public education regarding the virus; - poor communication infrastructure (leading to delayed medical response and public notification). The analysis of these conditions has helped many understand when, why and how Ebola disasters strike.

Precautions can therefore be taken by following the following preventive measures. More recent outbreaks have taken fewer lives because health officials have been introduced to these recommended and proper control techniques. - Improving sanitation, hygiene, and health care and education amongst the population. - Quarantining of Ebola patients (this is permitted but not required). - Supervising international travel.

- Improving communications for epidemiological education and notification, and coordination of health organizations. - Encouraging hospital personnel to use the patient isolation method called the 'barrier technique', which includes: 1) doctors and nurses wearing protective clothing like masks and gloves, 2) restricting the patients' visitors, 3) sterilization of reusable material, 4) disposing and incineration of disposable material right after their first and only use, and 5) all hard surfaces being cleaned with sanitizing solution. Little is known about this deadly virus, and there has been very slow but gradual advances in the studies of Ebola. A science milestone was created in 1976 when Dr. Frederick A. Murphy, the director for the National Center for Infectious Diseases (now of the University of California), made the first electron micrograph of the virus that killed hundreds in Zaire and Sudan at that time. The image was a magnification of 160 000 times of a most elegantly coiled organism (Fig. 1.2). But looks can deceive - and even kill.

The now-famous photograph made an appearance in the 1995 film Outbreak, and is currently splashed all over the website pages of many Ebola fans. But there's a lot more to discovery and investigation than merely capturing the virus on film. The image has only set the ball rolling for even more intensive research about the Ebola - there is still a lot more we have yet to know about it. For example, we are still unsure about its natural reservoir, where it lies dormant.

Studies are currently taking place in Cote d'Ivoire (Ivory Coast), Gabon and Zaire relating to this matter. So far, only monkeys have been identified as vectors as well as hosts of the Ebola virus. The Center of Disease Control and Prevention (CDC), World Health Organization (WHO) and the U.S. Army are all currently screening hundreds of various African animal species in search of other vectors. In the meantime, the genetic code for Ebola-Zaire has been completely sequenced, and the code for Ebola- Reston is almost completed. (These gene orders reaffirm their independence as a family.) In the April 16, 1996 issue of Proceedings of the National Academy of Sciences, U.S.A., Anthony Sanchez and his colleagues at the CDC reported their progress in genetic analysis of the Ebola virus. It seemed to them that the most important gene in the virus was the glycoprotein gene, which manufactures proteins that lie on the surface of the virus and are believed to transport the virus into the host cell.

Anthony Sanchez and his team had further analyzed the glycoprotein gene to reveal that filoviruses, besides destroying the cells they infect, might also kill their victims by overpowering the immune system. This could be one of the reasons why the Ebola virus is such a lethal pathogen. There have been comparisons between the HIV virus and the Ebola virus because of genetic and behavioral similarities, but research has proven that the Ebola virus has no association to the HIV virus in any way. Compared to other diseases like tuberculosis and hepatitis, the Ebola virus poses a rather limited threat to the public. It kills its victims so quickly that it cannot spread far. But this should not always be assumed, as pathogens have a frequent tendency to mutate, sometimes resulting in even deadlier versions.

The 1990's have seen monkeys being imported to the United States from the Philippines, and there have been several times when these imported monkeys have carried the Ebola-Reston virus. The most recent of these cases was in 1996, when two out of a hundred monkeys imported to Texas died from the virus and created panic amongst Texan citizens. Since then, the CDC has taken preventive measures by re-licensing importers and denying licenses to those whom did not possess proper facilities and staff training. The mystery of how an African virus ended up in the Philippines is still unsolved, and the case is still under study. The CDC's role in outbreak investigation has already lead them to send three medical scientists to Zaire to provide virus education within the hospital staff, and to provide advice and assistance in control and prevention, collect specimens for diagnostic testing, study the clinical course of the ill, and search for other possibly infected individuals. There is also a possible attempt to source the virus.

In a recent interview, Dr. Frederick A. Murphy had expressed concern over CDC's ability to respond to outbreaks and organize programs regarding infectious diseases, fundamentally due to poor financial status. He states that such programs "have been nibbled to death by inflation", subsequently leading to the loss of purchasing power by almost half. The CDC, along with other public health agencies, The National Academy of Sciences and the Institute of Medicine, have published plans on what is needed to control new and emerging diseases more efficiently. The plans focus on improving surveillance, laboratory diagnostics, communication and education.

However, as Dr Murphy stated, it is a pity that such good plans are constrained by tight budgets, which could probably get much worse. Thankfully, I have had no direct personal experiences with the Ebola virus. I still remember people going crazy over a book called "The Hot Zone"; I was unaware of it being about a virus called Ebola. It was only when a book called "Ebola: A Documentary Novel of its First Explosion" by William T. Close, M.D. hit the shelves that I actually sat up and took notice of the evil disease. The closest I have ever gotten to the virus is through the silver screen, when I watched the Ebola-associated film Outbreak when it was released several years ago. I remember witnessing the scenes featuring piles of corpses and the poor and dirty facilities of the hospitals in Africa.

But the scene which I was most horrified of was the one that featured a diagrammatic geographical presentation of how fast the Ebola virus would sweep across the United States. Contamination was represented by the color red. I always remember the army general counting down what would happen in the next 12, 24, and 36 hours. By 48 hours, the map of the U.S. had been soaked in red, like blood. I found it extremely scary as a young girl. However, after doing this project, I have realized that Hollywood tends to exaggerate reality.

In reality, the United States would have had more than efficient technology and education to handle such a virus, so it would be almost impossible for Ebola to conquer the entire continent. Dr. Frederick A. Murphy evaluated the movie and concluded that Outbreak has "created some false impressions" about the CDC's authority and the role of the Army in an epidemic situation. .".. The movie, ... with the Army taking over, is quite fictional". he said.

"I thought the early scenes in the Biosafety Level 1, 2, 3 and 4 labs looked pretty accurate. After that it became fiction, and I enjoyed it as fiction. We know a virus can't kill someone in an hour. The making of the antisera in a day was ludicrous".

I have received maximum benefit from choosing this topic because it has made me more aware of what the Ebola virus actually is and does, and it has corrected my false impressions of the virus. Before, the only thing I knew about Ebola was that it was a virus could cause an epidemic. Now I am proud to say that I know much more than that. I hope to educate others about the virus and create awareness of how deadly it is.

I now respect the Ebola virus because I have realized just how tiny a creature can cause such massive destruction; it is one of the very few creatures on earth that has the ability to conquer man. It ultimately proves that size does not matter. In the memorable words of Colonel Sam Daniels in the movie Outbreak: "You have to admire its simplicity. It's one billionth our size and it's beating us". The Ebola has created a deep, lasting impact on humankind. And it always will.

Bibliography

1) BBC Online News web 2) CNN Online "Possible Ebola Outbreak kills 63 in Congo" web "Two Monkeys Died From the Virus" web 3) The Killer Ebola web 4) Disease Information: Ebola Hemorrhagic Fever. Division of Viral and Rickettsia l Diseases, National Center for Infectious Diseases Centers for Disease Control and Prevention Public Health Service, U.S. Department of Health and Human Services web 5) Frequently-Asked-Questions about Ebola Primary contributions by Davina Ornstein and Kai Matthews with scientific review by Dr. Karl M. Johnson Copyright 1995, 1996 by Pragmatic a, Inc.
All rights reserved. web 6) Shaking the Ebola Tree web 7) Outbreak: the Deadly Truth web 8) EBOLA HAEMORRHAGIC FEVER Fact Sheet 103 Revised September 1997 WHO / OMS, 1998 web 9) Dr.
Frederick A. Murphy Talks about the Ebola Virus An Interview by Sean Henahan, Access Excellence web 10) History of Ebola Outbreaks web 11) Image of the Ebola Virus WHO / OMS, 1998 web 12) Map of Zaire, Africa web 13) Outbreak (1995) U.