Ebola Virus and Ebola Hemorrhagic Fever, Research Paper Example

Overview

Ebola virus (genus Ebolavirus, family Filoviridae) is known for its ability to cause Ebola hemorrhagic fever. In fact, being tied to various geographical locations, the term “Ebola” refers to a group of viruses, such as Ebola-Zaire, Ebola-Sudan, Ebola-Ivory Coast, and Ebola-Reston. According to World Health Organization, no cases of Ebola hemorrhagic fever outbreaks have been reported on the territory of the United States. Nonetheless, fatality ratio of 25 – 90 % in Sudan and Zaire shows that it may cause severe epidemic, which may turn to be not just local, but national problem. (World Health Organization, 2009) Incubation period of Ebola hemorrhagic fever varies from 2 to 21 days. During this period person can suffer from headache, various symptoms of regular fever, and weakness. This is often followed by vomiting, diarrhea, rash, impaired kidney and liver function, and in some cases, both internal and external bleeding. (World Health Organization, 2009). “One of the primary failures of the immune system in regards the Ebola virus, is the inability to activate T-cells early in the course of the infection resulting in an insufficient humoral response which include both antibody and cytokine responses.” (Takada, 2001) Ebola virus is easily transmitted during direct person-to-person contact and may cause a series of illnesses and even death.

Structure

All subtypes of Ebola virus have almost the same shape of prolonged capsule surrounded by filaments with a diameter of 80 nm, which may vary in length a lot. “The Ebola genome codes for 4 virion structural proteins (VP30, VP35, nucleoprotein, and a polymerase protein [L]) and 3 membrane-associated proteins (VP40, glycoprotein [GP], and VP24).” (King, 2008)

History

The first registered case of Ebola fever outbreak was registered on the territory of Zaire in 1976. Disease was spread rapidly among the patients of hospitals by means of sharing contaminated needles and direct physical contact. According to the Center for Disease Control and Prevention, 318 people were infected by Ebola virus. The death ratio was 88 % (280 people died). These events caused immediate reaction from the side of the government and scientists. (2009)

Outbreak of Ebola-Sudan occurred the same year in Nzara and Mairi areas. Virus was also spread by means of physical contact at heath care institutions. According to the Center for Disease Control and Prevention, 284 people were infected and 151 died.

For almost 25 years, Ebola fever outbreaks were rather small, as infected people were immediately isolated. Nonetheless, the most extreme case emerged in 2000-2001, when Ebola hemorrhagic disease was reported to become epidemic. 425 people were infected (with 53 % fatal ratio) in Gulu, Mbarara, and Masindi districts of Uganda. Virus was spread not only among medical care personnel and other patients, but also among relatives who attended funerals (Center for Disease Control and Prevention, 2009).

Transmission

Scientists are still searching for the source of Ebola hemorrhagic fever outbreaks. It is known that virus is easily transmitted through direct person-to-person contacts. Nonetheless, it was suggested that animals (gorillas, chimpanzees) are the carriers of Ebola. A multinational group of scientists has investigated five different Ebola fever outbreaks on the territory of Central Africa during 2001 – 2003. Tracking at least 10 epidemic chains, researchers concluded that first people suffering from Ebola fever were hunters, who handled either dead primates or antelopes. Scientists also noted high mortality rate among animals in the region right before epidemic. Sixteen dead animals were selected randomly to check whether their bodies were infected with Ebola virus. Total of fourteen animals (10 gorillas, 3 chimpanzees and 1 out of 3 antelopes) has positive results. Researchers believe that “Ebola virus appears to be introduced to humans and other animals through contact with animals that died recently from Ebola infection.” (Britigan, 2004) Secondly, seasonal investigations of mortality rates among animals may be helpful in identifying possible outbreaks of Ebola hemorrhagic fever.

According to World Health Organization, there are four primary ways of how Ebola viruses are transmitted from person to person. Direct physical contact with blood, secretions or body liquids of ill person is the most common one. Secondly, Ebola virus is often transmitted during burial ceremonies, where relatives also have direct contact with the dead body. Additionally, medical workers risk getting infected while treating patients without adequate infection control precautions. Several cases of getting sick with Ebola hemorrhagic fever occurred in Cote D’Ivoire, Congo and Gabon, while hunters handled infected gorillas, chimpanzees, and antelopes – both dead and alive. (World Health Organization, 2009)

Associates of the Center for Disease Control and Prevention have investigated possible risk factors for the family members of infected people. Out of 173 household contacts, only 28 people were infected with Ebola fever (18 %). This ratio increased progressively if exposure to body liquids and direct contacts occurred (Dowell, 1995). Therefore, it may be assumed that epidemic can be localized and stopped by means of isolation and intensive infection control precautions.

Symptoms

According to Tara Harper, there are 17 common symptoms, by which Ebola hemorrhagic fever can be detected (2005). Some of them can be detected during the first days of the incubation period, others can be noticed only after the first week passes by. Some of the early symptoms are listed below:

• Arthritis
• Bloody diarrhea
• Continuous fatigue
• Low backache and chest pain
• Continuous headache
• Discomfort
• Nausea
• Sore Throat
• Vomiting blood

These are some of the late symptoms:

• Bleeding from eyes, ears, and nose
• Gastrointestinal bleeding
• Conjunctivitis
• Genital Swelling
• Blindness
• Depression
• Stomach pain
• Coma

Diagnosis

A reverse transcriptase-polymerase chain reaction (RT-PCR) assay, immunohistochemical test, indirect fluorescent antibody test (IFAT), and serologic testing are used to identify Ebola virus.

Indirect fluorescent antibody test (IFAT) was one of the most commonly used for a long period of time. However, certain concerns in whether this test gave adequate results led to the development of other methods of identifying Ebola virus. Immunohistochemical test was “performed on formalin-fixed postmortem skin taken from patients who have died of Ebola hemorrhagic fever.” (King, 2008) This test gained popularity because it could be processed in small laboratories with limited containment systems.

“Serologic testing includes an antigen detection enzyme-linked immunosorbent assay (ELISA), an immunoglobulin M–capture ELISA using EBO-Z viral antigens harvested from infected Vero E6 cells, and an immunoglobulin G (IgG) ELISA using detergent-extracted Ebola antigens.” (King 2008) In fact, both IgM ELISA and IgG ELISA were developed as confirmatory tests to prove the results obtained in indirect fluorescent antibody test (IFAT). IgM ELISA test can be used to document Ebola hemorrhagic fever as it can be applied during the first 6 days of infection. Unfortunately, its results remain adequate only during incubation period. IgG ELISA results remain positive for a longer period of time, which makes this test to be superior in serologic testing.

A reverse transcriptase-polymerase chain reaction (RT-PCR) assay is a newly developed diagnostic technique, implemented by Centre International de Recherches Médicales de Franceville in Gabon. According to National Center for Biotechnology Information, RT-PCR assay is the most accurate and specific testing ever developed to identify Ebola infection. “Sensitivity of RT-PCR in identifying acute infection and early convalescence compared with antigen or IgM detection was 100% and 91% respectively, and specificity compared with antigen detection and IgM assay combined was 97%.” (Leroy, 2000).

Treatment

Supportive care is the only option used to treat patients infected with Ebola virus, as no cure is yet developed. In practice, associates of health care centers provide relief of Ebola symptoms, while the body of the patient is fighting infection. As any contact with Ebola virus is considered to be secondary (through infected animals and people), the source of the disease is still unidentified. Therefore, scientists are unable to study conditions, in which virus develops, and create vaccine strong enough to kill Ebola virus.

References

Britigan, B. (2004). Tracking the transmission of Ebola virus. Last retrieved on July 10, 2009 from http:/ /www.medscape.com/viewarticle/471039.

Dowell, S. (1995). Transmission of Ebola hemorrhagic fever: a study of risk factors in family members, Kikwit, Democratic Republic of the Congo. Last retrieved on July 10, 2009 from http:/ /www.ncbi.nlm.nih.gov/pubmed/9988169.

Harper, T. (2005). Virology Notes: Ebola. Last retrieved on July 10, 2009 from http:/ /www.tarakharper.com/v_ebola.htm.

King, J. (2008). Ebola Virus. Last retrieved July 10, 2009 from http:/ /emedicine.medscape.com/article/216288-overview.

Leroy, E. (2000). Diagnosis of Ebola haemorrhagic fever by RT-PCR in an epidemic setting. National Center for Biotechnology Information. Last retrieved on July 10, 2009 from http:/ /www.ncbi.nlm.nih.gov/pubmed/10686031.

Takada, A., Kawaoka, Y.B., (2001) The Pathogenesis of Ebola Hemorrhagic Fever.   Trends in Microbiology 2001. 9:506-511 Last retrieved on July 10, 2009 from http:/ /reviews.bmn.com/journals/atoz/browse?uid=TIM.etd00927_0966842x_v0009i10_00002201&node=TOC%40%40TIM%40011%4004%40011_04#sec_8.

World Health Organization. (2009). Ebola Hemorrhagic fever. Last retrieved on July 9, 2009 from http:/ /www.who.int/mediacentre/factsheets/fs103/en/.

Center for Disease Control and Prevention. (2009). Known cases and outbreaks of Ebola Hemorrhagic Fever, in Chronological Order. Last retrieved on July 9, 2009 from http:/ /www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/ebola/ebolatable.htm.