Disease
Ebola Virus

Author
Christine Sprinkel, BIOL 230, Spring 2009

Causative Agents
Ebola virus is one of two known Filoviruses that belong to the family Filoviride. Ebola Virus is a filamentous (def), enveloped, single-stranded, negative- sense RNA virus that replicates in host cells through budding. Most Ebola are uniform in diameter, 80 nanometers, but can vary in length, 1000-1400 nanometers (def). Virions (def) can appear coiled or branched.

Epidemiology
Ebola virus is responsible for several outbreaks of severe hemmoragic fever (def). It was first discovered in 1976 in Africa, along the Ebola River in Zaire and Sudan. Outbreaks have been sporadic, but usually isolated to central Africa. Currently, there is thought to be five different subtypes of Ebola virus; Ebola- Zaire, Ebola- Sudan, Ebola- Ivory Coast, Ebola- Bundibugyo, and Ebola- Restin. Mortality rate can varies among the subtypes with Ebola- Zaire having a mortality rate of up to 89%, and Ebola- Sudan, a mortality reat of up to 65%.  Ebola-Restin has been found  be pathogenic to primates only. Death usually occurs to hypovolemic shock and organ failure.

Transmission
Currently, there is no known reservoir for the Ebola virus although the virus is considered to be zoonotic (def). In 1996, a study in Zaire found that many insectivorous and fruit bats were living with Ebola virus without any clinical signs of the virus. Feces of both contained viable Ebola virus. This is often typical for a reservoir species. It has also been found that many hunters have become infected with the virus after  handling dead primates. Primary infections of Ebola seem to come from animal to person to contact. Secondary infections, which can become epidemic, seem to spread from person to person contact. Ebola  is presumed to spread through direct contact with bodily fluids, infected tissues, or even objects that have been contaminated with infected secretions. Incubation of Ebola varies greatly and can be anywhere from 2-21 days.

Signs and Symptoms
Primary infections from Ebola virus usually become symptomatic within 3-8 days of exposure. Secondary infections tend to take slightly longer. Initial symptoms are sudden and can include severe headache, myalgias (def), fever, anorexia, and asthenia (def). Gastrointestinal disturbances; vomiting, nausea, diarrhea soon follow. Conjunctivitis (def) and bleeding from GI tract and mucous membranes also occur in about 50% of cases.  Sometimes a rash can be seen. Hiccups have also been noted in several terminal cases. One study found that tachypnea (def) was a disseminating sign in which 0%  was found in survivors of the virus, and 37% was found in those that eventually died.
     
Ebola virus has demonstrated to be present in tissues and bodily fluids of those that do survive for several weeks to months  after clinical signs disappear.

Prevention and Treatment
Because Ebola is so highly contagious, isolation and strict barrier precautions are necessary in the prevention of epidemic outbreaks. Double gloves, fluid proof gowns, coverings for both legs and shoes, face shields and eye protection should be worn at all times when dealing with suspected or confirmed patients. Objects that have come in contact with patients, and even bodies of expired patients need to be treated with the same precautions to prevent spreading.

To date, there is no specific therapy available to prevent Ebola. Supportive care is usually given, keeping patient’s fluids, and electrolytes in balance, administering of oxygen, and monitoring of blood pressure. Giving convalescent plasma  to infected patients, from those who have survived Ebola, has shown some promise, however other common antiviral treatments such as Ribavirin and Interferon, have shown to be ineffective in treatment.

Experimental DNA vaccines are ongoing. These mainly focus on attacking the envelope Gp and nucleocapsid protein genes of the Ebola virus.

Bibliography

CDC. National Center for Disease Control and Prevention. Ebola Questions and Answers. Retrieved April 16, 2009 from http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/ebola/qa.

CDC. National Center for Disease Control and Prevention.  Filoviruses. Retrieved April 16, 2009 from http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/filoviruses.htm

King, John W. M.D. Ebola Virus; Differential Diagnosis and work-up. April 2, 2008. emedicine.medscape.com. Retrieved April 16, 2009 from http://emedicine.medscape.com/article/216288-diagnosis

Research Today. About Ebola Virus. Retrieved April 16, 2009 from http://ebolavirus.researchtoday.net/about-ebolavirus.htm