Of the many human pathogens, the Ebola virus is one with a very high mortality rate and no cure. The name “Ebola” comes from a small river in Zaire (now known as the Democratic Republic of Congo) where the virus was first isolated. The Ebola virus causes a lethal illness known as Ebola hemorrhagic fever. Four subtypes of the Ebola viruses are named after the location in which they were first identified and include Zaire, Sudan, Ivory Coast, and Reston. Zaire, Sudan, and Ivory Coast, all found in Central Africa, cause the severe viral hemorrhagic fever and those who contract these types suffer a high morality rate.
The fourth, known as Reston, is not known to cause illness in humans but is highly pathogenic in primates. The Zaire and Sudan were first recognized in 1976 when they were causing simultaneous outbreaks in Zaire and Sudan. The epidemic in Zaire involved 278 known cases, almost all of which were contracted through contaminated hospital equipment or contact with infected patients. The morality rate in the Zaire epidemic was nearly 90 percent. In the same year, a separate epidemic in Sudan involved nearly 300 cases with more than 50 percent mortality.
Outbreaks since 11 Calkins then have included Cote d’Ivorie (the Ivory Coast) and another outbreak in Zaire during 1995. Both cases had a mortality rate of over 77 percent. The Zaire is still considered the most deadly of the four subtypes of the Ebola virus. The Reston subtype of the Ebola virus was first identified in Reston, Virginia in the year 1989. Outbreaks of the Reston occurred in the United States between the years 1989 and 1996, however no infected humans showed symptoms of the virus.
The virus is believed to have been circulating in domestic pigs in the Philippines, possibly even before the 1989 outbreaks in the United States. While the pigs did not develop any illness, the Reston strain is considered to be the cause of sudden death for a group of Asian macaques monkeys in 1990.
It was concluded that the Reston does not cause illness in humans but is deadly for non-human primates. Altogether, Ebola has caused nearly 2000 cases and roughly 1250 deaths since its identification in Zaire during the summer of 1976. The incubation period of Ebola virus can last anywhere between 2 and 21 days. Initial symptoms of Ebola virus include high fever, headache, chills, myalgia, sore throat, red itchy eyes, and malaise.
The initial symptoms of Ebola virus resemble less fatal viruses such as malaria, typhoid fever, dysentery, and influenza. These viruses are prevalent in the same geographical areas as the Ebola virus, so patients who contract it are often mistreated. Later symptoms that occur include bloody feces, vomiting blood, gastrointestinal bleeding 22 Calkins from the mouth and rectum, and even internal bleeding in the brain. In some cases, brain hemorrhaging in Ebola patients can lead to depression, seizures, and delirium. After two weeks of contracting the virus, the patient will either recover fully or experience multi-organ failure, leading to slow and painful death.
The exact cause of death for most Ebola patients is hypovolemic shock or organ failure. Unsanitary hospital conditions were to blame for the outbreaks in Africa where hospital hygiene is limited. Most humans that become infected with Ebola virus contract it through direct contact with patients or by handling the deceased. The virus can enter the host through mucosal surfaces such as the mouth or skin or through ingestion of infected animals. In one case during 1995, nineteen men in the African country of Gabon contracted the Ebola virus from a dead chimpanzee they found in the forest and brought back to their village.
Thirteen of them died from Ebola hemorrhagic fever. Since then, the Gabonese government, along with others, have issued public safety announcements that warn against coming in contact with sick or dead animals in the forests and to take precautions against infected individuals’ blood. The Reston strain has been transmitted through the air between primates, but airborne transmission has not been blamed for Zaire, Sudan, or other Ebola strains in humans. The Ebola virus is a member of the Filovirus family, which are RNA viruses.
Along with Marburg, the Filoviruses are among the least 33 Calkins understood of all viruses. Their natural hosts are unknown, however some believe they originated in primates. The virus itself is 19 kb long and includes seven open reading frames that encode the following seven proteins: virion envelope glycoprotein, nucleoprotein, two matrix proteins, two nonstructural proteins, and the viral polymerase. During infection of the virus, host and viral proteins both contribute to the pathogenesis of the Ebola virus. The morphology of the Ebola virus is classified as helical.
The Ebola virus replicates at an unusually high rate, which overwhelms the protein synthesis of infected cells and the host’s immune defenses. The body responds to an Ebola virus infection through adaptive immune and inflammatory systems simultaneously, resulting in monocytes and macrophages becoming targets. The direct infection of monocytes and macrophages causes the release of cytokines, which are associated with inflammation and fever. Whether or not the cytokines are damaging or protective depends on their profile and the infected person’s individual immune response.
Infection of the endothelial cells damage the endothelial barrier, and together with the release of cytokines, leads to the loss of vascular integrity. Since the integrity of blood vessels is critical to vascular homeostasis, failure of this system accounts for the serious symptoms such as massive hemorrhaging, edema, and inflammation. 44 Calkins The progression of disease in animals like pigs and primates closely resemble those of the human body. In order to develop a cure for the Ebola virus, a study was performed in Manitoba, Canada to understand the Ebola virus by infecting pigs with the Zaire strain. Six
piglets were infected through their nasal cavities, eyes, and mouth. Additionally, two other pigs that were part of the study were included as a control and were not inoculated. The inoculated pigs in the study developed a fever four days after inoculation, which lasted an additional seven days. The pigs stopped eating, lost interest in human presence and activity, stopped interacting with other pigs, and preferred not to stand up or move around in their cages. The pigs suffered prominent respiratory effects that increased their breathing rate from 35 breaths per minute to around 80 breaths per minute.
The multi-organ failure of which the Ebola virus is known for was observed after just a few days. The lymph nodes in the pigs’ lungs became hemorrhagic and inflamed. This caused loss of alveolar spaces, disabling the pigs’ ability to breath properly and accounting for increased breathing rate. More pathological changes were observed in the pigs’ hearts, where the right atrium was hemorrhagic. Researchers at Thomas Jefferson University in Philadelphia, PA developed a vaccine that was based on the well-understood rabies virus.
Since rabies is also a helical virus, vaccines for it proved to protect against Ebola infection as well. In total, three vaccines that are used to treat rabies have 55 Calkins proved to protect against the Ebola virus in animals. Researchers have demonstrated that a dual-purpose vaccine is possible for humans to protect against both rabies and Ebola virus. While a vaccine for Ebola prevention is underway, the cure for the virus is still not available.
Time is the only thing that an infected individual can rely on to survive both Ebola and Marburg viruses. When Ebola symptoms develop, supportive care is the only thing that can be offered from healthcare providers while the body fights the infection.
Such supportive care includes oxygen delivery, antibiotics to prevent further infections, and other medications to control fever, blood pressure, and promote clotting, which can counter severe blood loss. Any body fluids from an infected patient, including urine, saliva, blood, and stool, must be handled appropriately as they can potentially infect others. Additionally, patients who die due to Ebola infection must be disposed of properly and quickly with little contact as possible as they can easily infect handlers of the corpse. As more studies are performed, researchers hope to find a cure for the Ebola hemorrhagic fever that is caused by the Ebola virus.
The CDC reports outbreaks as recent as 2012 in both Uganda and the Democratic Republic of Congo. Now in the era of increased global travel, spreading of the Ebola virus to different populated areas is even more of a frightening possibility than it was in the 1970’s. When large outbreaks do occur, isolation of infected patients is becoming more 66 Calkins difficult since the disease is difficult to identify. However, with each outbreak researchers are learning more about the virus.
The symptoms of the Ebola virus are among the worst of all human pathogens, and researchers hope a cure can be found within the near future. 77 Calkins.
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Print. McCormick , Joseph. “Ebola Virus Ecology . ” Oxford Journals .N. p. , 1 Dec. 2001. Web. 28 Feb. 2014. <http://jid. oxfordjournals. org/content/190/ Mosby’s Dictionary of Medicine, Nursing, & Health Professions. St. Louis : Elsevier Health Sciences, 2012. Print. Sullivan , Nancy. “Ebola Virus Pathogenesis . ” Journal of Virology. N. p. , 1 Mar. 2005. Web. 28 Feb. 2014. <http://jvi. asm. org/content/77/18/9733>. Vayas, Jatin. “Ebola hemorrhagic fever: MedlinePlus Medical Encyclopedia. ” U. S National Library of Medicine. U. S. National Library of Medicine, n. d. Web. 28 Feb. 2014. <http://www. nlm. nih. gov/medlineplus/ency/article/001339. htm>.