Name: LaTanya J. Gary

Lab Section: CRB-8

Ebola Virus

Causative Agents

     The Ebola virus originates from Filoviruses.  Along with the Marburg virus, they encompass the family (group) Filoviride.  Ebola is an enveloped enclosed, single-stranded, filamentous (def), unsegmented, negative-sense, rribonucleic acid virus with the capability of reproducing by way of budding (def).  Although the virus can vary in length, some can grow as long as 14,000 nm (def) with the standard being 80 nm in diameter.  On average, they are approximately 920 nm long.  These virions (def) resemble coiled snails, six’s, or U’s and may appear with or without visible branching.

Epidemiology

     The Ebola virus is one of 18 viruses capable of initiating hemorrhagic fever (def).  The virus appeared first in 1972, but it was not identified until 1976, when two epidemics transpired in Zaire and the southern region of Sudan.  It received its title based on the first sight of recognition, the Ebola River located in Democratic Republic of the Congo (previously Zaire) in Africa.  Currently, there are five subtypes: Ebola-Zaire, Ebola-Sudan, Ebola-Bundibugyo, Ebola-Ivory Coast and finally, Ebola-Reston.  This causes infection in a non-human primate.  Ebola-Reston was discovered in crab-eating Macaque (def) transported from the Philippines to a research facility located in Reston, Virginia.

     Globally, the mortality rate is exceptionally high and can differ from 50% to 89% based on the strain of Ebola.  Ebola-Zaire, the most lethal form of the five subtypes, has a mortality rate of 89%, followed by Ebola-Sudan with an estimated mortality rate of 41 to 65%.

Transmission

     Ebola is transmitted through the exchange and/or direct contact of bodily fluids such as saliva, blood, semen, virginal secretions or tissue infected with the virus.  

     Primary exposure stems from individuals traveling to or working in Ebola-endemic areas or African rain forests.  It is thought that the original transmission to the human population stemmed from contact with infected primates. However, they are not natural reservoirs.  The exact reservoir is unknown.  Yet, fruit bats are suspected as a natural source for the viruses because they not only carry the virus but are also asymptomatic, making those excellent natural reservoirs.

     Secondary exposure involves human-to-human or zoonotic (def) contact.  The strains originating in Africa that caused major outbreaks, stemmed from caregivers such as family members or medical personnel or (nosocomial transmission (def)) involved in the preparation of deceased relatives or patients for burial.

     Furthermore, outbreaks of the virus can be traced to individuals and/or animal care workers who handled dead primates or provided care for primates such as gorillas or chimpanzees.

Signs and Symptoms

     Primary strains originating in Africa have a typical 3-8 day incubation period, while secondary cases are a bit longer.  Yet, incubation periods from 19 to as long as 21 days have been reported.

     Clinical symptoms are sudden with early onset of symptoms such as severe headaches, arthralgias or myalgias (def), hemorrhagic fever (def) with or without chills, anorexia, asthenia (def), and sore throat.  Secondly, gastrointestinal symptoms such as diarrhea (85%), nausea and/or vomiting (68-73%) and abdominal pain (65%) occur.  Thirdly, problems such as bleeding from the gastrointestinal tract and mucous membranes (40-50%).  Then the eyes, nose and/or mouth begin to bleed, followed by a hemorrhagic rash that covers the body. This occurs in approximately 15% of all patients.

     Patients who are terminally ill experience tachypneic (def), anuric (def) and are often comatosed.  Most of them expire due to hypovolemic shock (def) or MSOF (def) between 2 to 21 days after the initial infection.  Myocarditis and pulmonary edema are also seen in the later stages of the disease.  In 1976 and 1995 outbreaks, hiccups were noted in fatal cases of Ebola.  The exact mechanism or method is unknown. 

     Some patients are able to survive after 14 days, due to a reduction in fever.  However, the Ebola virus is still present in tissues and bodily fluids several weeks to months after all clinical signs dissipate.  The ELISA test is used to diagnose patients using urine or saliva samples.  However, this test does not yield accurate results.

     It is uncertain as to whether or not specific long-term effects or complications exist from the infection as it has not been studied long enough in survivors.

Prevention and Treatment

     During the initial stage, the virus isn’t necessarily communicable or contagious.  However, as it progresses, bodily fluids from diarrhea, vomiting, bleeding or infected tissue symbolize serious risk.  Immediate and strict enforcement of sterilization techniques, patient isolation, barrier procedures, and the use of medically approved disposable gloves, goggles, face masks and gowns for medical personnel and visitors, will decrease the rate of transmission.  Certain solvents, detergents, and various disinfectants as well as gamma or ultraviolet radiation are proven to harm or kill the virus on surfaces.

     To date, there are no successful human vaccines or therapies available for prevention or treatment of Ebola.  Treatment is supportive, yet minimally invasive, which includes the stabilization electrolytes to prevent dehydration, restoration of clotting factors to stop or reduce bleeding, sustaining oxygen levels, restoring blood loss and stopping/decreasing severe infections.

     In March of 2009, a researcher was accidentally pricked with a needle containing Ebola virus particles.  The researcher was given the vaccine as part of her emergency treatment. She failed to develop Ebola hemorrhagic fever and no harmful side effects were reported.  However, she was not tested for the virus, so as a result; researchers can not confirm the vaccines effectiveness.  Researchers are working with DNA based vaccines, they hope to develop an effective vaccine soon.

Bibliography
CDC. National Center for Disease Control and Prevention. Ebola Questions and Answers.  Retrieved April 9, 2010 from http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/ebola/qa.htm
CDC. National Center for Disease Control and Prevention. Ebola Hemmoragic Fever Information Packet.  Retrieved April 9, 2010 from http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/Fact_Sheets/Ebola_Fact_Booklet.pdf
Wikipedia. The Free Encyclopedia. Ebola. Retrieved April 13, 2010 from http://en.wikipedia.org/wiki/Ebola
Slonczewski, Joan.  Ebola Virus. BIOL 191 Microbiology, 2009. Microbe Wiki. Retrieved April 13, 2010 from http://microbewiki.kenyon.edu/index.php/Ebola_virus
King, John W. M.D. Ebola Virus; Differential Diagnosis and Work-up. April 2, 2008. emedicine.medscape.com. Retrieved April 14, 2010 from http://emedicine.medscape.com/article/216288-overview