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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:  Michael Maddaleni, B.S.; Guillermo Rodriguez Nava, M.D. [2]; Yazan Daaboul, M.D.

## Overview[edit | edit source]

Ebola virus was first discovered in 1976 when two simultaneous outbreaks occurred in Zaire and Sudan. The first description of Ebola virus was made by Ngoy Mushola in Yambuku, Zaire during the 1976 outbreak. During the outbreak, Peter Piot analyzed blood samples of an infected Belgian nun in Zaire and was the first to describe the virus morphology using electron microscopy. The Ebola virus was named after the Ebola River Valley in the Democratic Republic of the Congo (formerly Zaire).[1] Approximately 14 outbreaks of Ebola virus have been described since its discovery. The 2013-2014 outbreak marks the largest Ebola outbreak, involving Africa, Asia, Europe, and America and making the virus a worldwide disease.

## Historical Perspective[edit | edit source]

### Discovery[edit | edit source]

* The Ebola virus was first discovered in 1976 following two simultaneous outbreaks of Ebola hemorrhagic fever between June and November in Zaire and between August and November in Sudan.[2][3]
* Nurse Mayinga N'Seka, a nurse in Zaire, is thought to be the index case in the first recognized Ebola epidemic in 1976. She was believed to be the only patient infected via airborne transmission of the Ebola virus.
* The fist description of Ebola virus infection was made by Ngoy Mushola, who recorded the first case in Yambuku town in Zaire. In Dr. Mushola's daily log, he stated

“  | The illness is characterized by a high temperature of about 39 °C,hematemesis, bloody diarrhea, retrosternal abdominal pain, prostration with "heavy" articulations, and rapid evolution death after a mean of three days...  | ”

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* During the outbreak, blood samples of infected Belgian nuns in Zaire were refrigerated in non-secure thermos and sent to Europe for analysis. Peter Piot was the first to analyze and describe Ebola virus morphology using electron microscopy. He noted the presence of long, worm-like agents that resemble the Marburg virus that was associated with the death of laboratory workers in Germany.
* The virus was then named after the Ebola river located in the town Yambuku, Democratic Republic of the Congo (formerly Zaire), which is the site of the first recognized Ebola outbreak.
* The first outbreaks occurred almost simultaneously in Sudan on June - November 1976 due to the so-called Sudan ebolavirus and in the Democratic Republic of Congo (formerly Zaire) on August - November 1976 due the so-called Ebola Zaire.
* Ever since the initial discovery, 5 strains of Ebola virus have been identified.

### Spread[edit | edit source]

* The first two recorded outbreaks of Ebola virus occurred in 1976, followed by a third outbreak in 1979.[4]
* For 15 years, no outbreaks of Ebola virus were recorded, until Ebola re-emerged in 1994 when a Swiss ethnologist was infected during a chimpanzee autopsy in Tai National Park in Ivory Coast.[5][6] During the same period, 3 other outbreaks occurred in Mekouka, Mayibout, and Booue in Gabon between 1994 and 1997.[7][8][9]
* The period between 2000 and 2004 was remarkable for the emergence of multiple outbreaks among humans as well as among animals (gorillas and chimpanzees) in Gabon, the Republic of Congo, and Uganda.[10] At least 20 outbreaks were reported between the years 1976 (time of discovery) and 2013.
* In March 23 2014, the Ministry of Health of Guinea notified the World Health Organization (WHO) of an emerging outbreak. The outbreak rapidly evolved to become the largest Ebola outbreak since its discovery in 1976. The first case of the Ebola outbreak was reported in Guinea in December 2013. The index case was thought to be a 2-year-old boy. The 2014 outbreak then involved Liberia, Sierra Leone, Senegal, and Nigeria before the virus was spread to Europe, Asia, and America, making Ebola virus a worldwide threat. On August 8 2014, the WHO declared the Ebola epidemic to be a Public Health Emergency of International Concern (PHEIC).[11]

### Major Outbreaks[edit | edit source]

Until recently, Ebola outbreaks have been restricted to Africa, with the exception of Reston ebolavirus. The International Committee on Taxonomy of Viruses currently recognizes four species of the Ebola: Zaire virus (ZEBOV), Sudan ebolavirus (SEBOV), Reston ebolavirus (REBOV), and Cote d'Ivoire ebolavirus (CIEBOV).

Known Cases and Outbreaks of Ebola Hemorrhagic Fever, in Chronological Order[12] Year(s) | Country | Ebola subtype | Reported number of human cases | Reported number (%) of deaths among cases | Situation

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1976 | Zaire (Democratic Republic of the Congo - DRC) | Ebola virus | 318 | 280 (88%) | Occurred in Yambuku and surrounding area. Disease was spread by close personal contact and by use of contaminated needles and syringes in hospitals/clinics. This outbreak was the first recognition of the disease.
1976 | Sudan (South Sudan) | Sudan virus | 284 | 151 (53%) | Occurred in Nzara, Maridi and the surrounding area. Disease was spread mainly through close personal contact within hospitals. Many medical care personnel were infected.
1976 | England | Sudan virus | 1 | 0 | Laboratory infection by accidental stick of contaminated needle.
1977 | Zaire | Ebola virus | 1 | 1 (100%) | Noted retrospectively in the village of Tandala.
1979 | Sudan (South Sudan) | Sudan virus | 34 | 22 (65%) | Occured in Nzara, Maridi. Recurrent outbreak at the same site as the 1976 Sudan epidemic.
1989 | USA | Reston virus | 0 | 0 | Ebola-Reston virus was introduced into quarantine facilities in Virginia and Pennsylvania by monkeys imported from the Philippines.
1990 | USA | Reston virus | 4 (asymptomatic) | 0 | Ebola-Reston virus was introduced once again into quarantine facilities in Virginia, and Texas by monkeys imported from the Philippines. Four humans developed antibodies but did not get sick.
1989-1990 | Philippines | Reston virus | 3 (asymptomatic) | 0 | High mortality among cynomolgus macaques in a primate facility responsible for exporting animals in the USA.
Three workers in the animal facility developed antibodies but did not get sick.
1992 | Italy | Reston virus | 0 | 0 | Ebola-Reston virus was introduced into quarantine facilities in Sienna by monkeys imported from the same export facility in the Philippines that was involved in the episodes in the United States. No humans were infected.
1994 | Gabon | Ebola virus | 52 | 31 (60%) | Occured in Mékouka and other gold-mining camps deep in the rain forest. Initially thought to be yellow fever; identified as Ebola hemorrhagic fever in 1995.
1994 | Ivory Coast | Taï Forest virus | 1 | 0 | Scientist became ill after conducting an autopsy on a wild chimpanzee in the Tai Forest. The patient was treated in Switzerland.
1995 | Democratic Republic of the Congo (formerly Zaire) | Ebola virus | 315 | 250 (81%) | Occured in Kikwit and surrounding area. Traced to index case-patient who worked in forest adjoining the city. Epidemic spread through families and hospitals.
1996 (January-April) | Gabon | Ebola virus | 37 | 21 (57%) | Occured in Mayibout area. A chimpanzee found dead in the forest was eaten by people hunting for food. Nineteen people who were involved in the butchery of the animal became ill; other cases occured in family members.
1996-1997 (July-January) | Gabon | Ebola virus | 60 | 45 (74%) | Occurred in Booué area with transport of patients to Libreville. Index case-patient was a hunter who lived in a forest camp. Disease was spread by close contact with infected persons. A dead chimpanzee found in the forest at the time was determined to be infected.
1996 | South Africa | Ebola virus | 2 | 1 (50%) | A medical professional traveled from Gabon to Johannesburg, South Africa, after having treated Ebola virus-infected patients and thus having been exposed to the virus. He was hospitalized, and a nurse who took care of him became infected and died.
1996 | USA | Reston virus | 0 | 0 | Ebola-Reston virus was introduced into a quarantine facility in Texas by monkeys imported from the Philippines. No human infections were identified.
1996 | Philippines | Reston virus | 0 | 0 | Ebola-Reston virus was identified in a mokey export facility in the Philippines. No human infections were identified.
1996 | Russia | Ebola virus | 1 | 1 (100%) | Laboratory contamination
2000-2001 | Uganda | Sudan virus | 425 | 224 (53%) | Occurred in Gulu, Masindi, and Mbarara districts of Uganda. The three most important risks associated with Ebola virus infection were attending funerals of Ebola hemorrhagic fever case-patients, having contact with case-patients in one's family, and providing medical care to Ebola case-patients without using adequate personal protective measures.
October 2001-March 2002 | Gabon | Ebola virus | 65 | 53 (82%) | Outbreak occured over the border of Gabon and the Republic of the Congo.
October 2001-March 2002 | Republic of Congo | Ebola virus | 57 | 43 (75%) | Outbreak occurred over the border of Gabon and the Republic of the Congo. This was the first time that Ebola hemorrhagic fever was reported in the Republic of the Congo.
December 2002-April 2003 | Republic of Congo | Ebola virus | 143 | 128 (89%) | Outbreak occurred in the districts of Mbomo and Kéllé in Cuvette Ouest Département.
November-December 2003 | Republic of Congo | Ebola virus | 35 | 29 (83%) | Outbreak occured in Mbomo and Mbandza villages located in Mbomo distric, Cuvette Ouest Département.
2004 | Sudan (South Sudan) | Sudan virus | 17 | 7 (41%) | Outbreak occurred in Yambio county of southern Sudan. This outbreak was concurrent with an outbreak of measles in the same area, and several suspected EHF cases were later reclassified as measeles cases.
2004 | Russia | Ebola virus | 1 | 1 (100%) | Laboratory contamination.
2007 | Democratic Republic of Congo | Ebola virus | 264 | 187 (71%) | Outbreak occurred in Kasai Occidental Province. The outbreak was declared over November 20. Last confirmed case on October 4 and last death on October 10.
December 2007-January 2008 | Uganda | Bundibugyo virus | 149 | 37 (25%) | Outbreak occurred in Bundibugyo District in western Uganda. First reported occurance of a new strain.
November 2008 | Philippines | Reston virus | 6 (asymptomatic) | 0 | First known occurrence of Ebola-Reston in pigs. Strain closely similar to earlier strains. Six workers from the pig farm and slaughterhouse developed antibodies but did not become sick.
December 2008-February 2009 | Democratic Republic of the Congo | Ebola virus | 32 | 15 (47%) | Outbreak occurred in the Mweka and luebo health zones of the Province of Kasai Occidental.
May-11 | Uganda | Sudan virus | 1 | 1 (100%) | The Ugandan Ministry of Health informed the public that a patient with suspected Ebola Hemorrhagic fever died on May 6, 2011 in the Luwero district, Uganda. The quick diagnosis from a blood sample of Ebola virus was provided by the new CDC Viral Hemorrhagic Fever laboratory installed at the Uganda Viral Research Institute (UVRI).
June-October 2012 | Uganda | Sudan virus | 11* | 4* (36.4%) | Outbreak occurred in the Kibaale District of Uganda. Laboratory tests of blood samples were conducted by the UVRI and the U.S. Centers for Disease Control and Prevention (CDC).
June-November 2012 | Democratic Republic of the Congo | Bundibugyo virus | 36* | 13* (36.1%) | Outbreak occurred in DRC’s Province Orientale. Laboratory support was provided through CDC and the Public Health Agency of Canada (PHAC)’s field laboratory in Isiro, and through the CDC/UVRI lab in Uganda. The outbreak in DRC has no epidemiologic link to the near contemporaneous Ebola outbreak in the Kibaale district of Uganda.
November 2012-January 2013 | Uganda | Sudan virus | 6* | 3* (50%) | Outbreak occurred in the Luwero District. CDC assisted the Ministry of Health in the epidemiologic and diagnostic aspects of the outbreak. Testing of samples by CDC's Viral Special Pathogens Branch occurred at UVRI in Entebbe.
March 2014-Present | Guinea, Liberia, and Sierra Leone | Ebola virus | 9936 | 4878 (49.1%) | Outbreak across Guinea, northern Liberia, and now eastern Sierra Leone.
May 2017  | Democratic Republic of the Congo  | Not confirmed  | 9  | 1 (1.1%)  | In May 12, 2017, WHO declared a lab confirmed case in Bas-Uele region in the northeast Congo. Nine cases were hospitalized for hemorrhagic fever and three of them died. Only one case was confirmed to have Ebola virus.

Despite being a serious situation, it's considered a good sign that the outbreak struck in a remote and forested region

## References[edit | edit source]

1. ↑ Bardi, Jason Socrates (2002). "Death Called a River". Scribbs Research Institute. 2 (1). Retrieved 2006-12-08.
2. ↑ "Ebola haemorrhagic fever in Zaire, 1976". Bull World Health Organ. 56 (2): 271–93. 1978. PMC 2395567. PMID 307456.CS1 maint: PMC format (link)
3. ↑ "Ebola haemorrhagic fever in Sudan, 1976. Report of a WHO/International Study Team". Bull World Health Organ. 56 (2): 247–70. 1978. PMC 2395561. PMID 307455.CS1 maint: PMC format (link)
4. ↑ Baron RC, McCormick JB, Zubeir OA (1983). "Ebola virus disease in southern Sudan: hospital dissemination and intrafamilial spread". Bull World Health Organ. 61 (6): 997–1003. PMC 2536233. PMID 6370486.CS1 maint: Multiple names: authors list (link) CS1 maint: PMC format (link)
5. ↑ Le Guenno B, Formenty P, Formentry P, Wyers M, Gounon P, Walker F; et al. (1995). "Isolation and partial characterisation of a new strain of Ebola virus". Lancet. 345 (8960): 1271–4. PMID 7746057.CS1 maint: Explicit use of et al. (link) CS1 maint: Multiple names: authors list (link)
6. ↑ Formenty P, Hatz C, Le Guenno B, Stoll A, Rogenmoser P, Widmer A (1999). "Human infection due to Ebola virus, subtype Côte d'Ivoire: clinical and biologic presentation". J Infect Dis. 179 Suppl 1: S48–53. doi:10.1086/514285. PMID 9988164.CS1 maint: Multiple names: authors list (link)
7. ↑ Khan AS, Tshioko FK, Heymann DL, Le Guenno B, Nabeth P, Kerstiëns B; et al. (1999). "The reemergence of Ebola hemorrhagic fever, Democratic Republic of the Congo, 1995. Commission de Lutte contre les Epidémies à Kikwit". J Infect Dis. 179 Suppl 1: S76–86. doi:10.1086/514306. PMID 9988168.CS1 maint: Explicit use of et al. (link) CS1 maint: Multiple names: authors list (link)
8. ↑ Georges AJ, Leroy EM, Renaut AA, Benissan CT, Nabias RJ, Ngoc MT; et al. (1999). "Ebola hemorrhagic fever outbreaks in Gabon, 1994-1997: epidemiologic and health control issues". J Infect Dis. 179 Suppl 1: S65–75. doi:10.1086/514290. PMID 9988167.CS1 maint: Explicit use of et al. (link) CS1 maint: Multiple names: authors list (link)
9. ↑ Amblard J, Obiang P, Edzang S, Prehaud C, Bouloy M, Guenno BL (1997). "Identification of the Ebola virus in Gabon in 1994". Lancet. 349 (9046): 181–2. doi:10.1016/S0140-6736(05)60984-1. PMID 9111553.CS1 maint: Multiple names: authors list (link)
10. ↑ Pourrut X, Kumulungui B, Wittmann T, Moussavou G, Délicat A, Yaba P; et al. (2005). "The natural history of Ebola virus in Africa". Microbes Infect. 7 (7–8): 1005–14. doi:10.1016/j.micinf.2005.04.006. PMID 16002313.CS1 maint: Explicit use of et al. (link) CS1 maint: Multiple names: authors list (link)
11. ↑ Briand S, Bertherat E, Cox P, Formenty P, Kieny MP, Myhre JK; et al. (2014). "The international Ebola emergency". N Engl J Med. 371 (13): 1180–3. doi:10.1056/NEJMp1409858. PMID 25140855.CS1 maint: Explicit use of et al. (link) CS1 maint: Multiple names: authors list (link)
12. ↑ "CDC Chronology of Ebola Hemorrhagic Fever Outbreaks".