Transmission of the ebolaviruses between natural reservoirs and humans is rare, and outbreaks of Ebola virus disease are often traceable to a single case where an individual has handled the carcass of a gorilla, chimpanzee, bats,[9] or duiker.[10] The virus then spreads person-to-person, especially within families, in hospitals, and during some mortuaryrituals where contact among individuals becomes more likely.[11]
Nigeria was the first country in western Africa to successfully curtail the virus, and its procedures have served as a model for other countries to follow.[14][15][16]
Events
The information in the following tables comes from the World Health Organization (WHO). This data excludes all laboratory personnel cases, Reston virus cases (since they are all asymptomatic), and suspected cases.[17] For a complete overview, those cases are included below with footnotes and supporting sources.
Occurred in Nzara (the source town), Maridi, Tumbura, and Juba (cities in present-day South Sudan). The index cases were workers in a cotton factory. The disease was spread by close contact with an acute case, usually from patients to their nurses. Many medical care personnel were infected.[18]
Occurred in Yambuku and surrounding areas in what was then Zaire (present-day Democratic Republic of the Congo DRC). It spread through personal contact and by use of contaminated needles and syringes in hospitals and clinics.[19]
Occurred in Kikwit and surrounding areas. The outbreak was traced to a patient who worked in a forest adjoining the city. The epidemic spread through families and hospital admissions.[22][23]
The first strain Occurred in the village of Mayibout 2 and neighboring areas. A chimpanzee found dead in the forest was eaten by villagers hunting for food. Nineteen people involved in the butchery of the animal became ill, and other cases occurred in their family members.[21]
The last strain Occurred in the Booué area with transport of patients to Libreville. The index case-patient was a hunter who lived in a forest timber camp. The disease was spread by close contact with infected persons. A dead chimpanzee found in the forest at the time was determined to be infected.[21]
Occurred in the Gulu, Masindi, and Mbarara districts of Uganda. The three greatest risks associated with Sudan virus infection were attending funerals of case-patients, having contact with case-patients in one's family, and providing medical care to case-patients without using adequate personal protective measures.[24] Victims included Matthew Lukwiya.
The first strain Occurred on both sides of the border between Gabon and the Republic of the Congo (RC). This outbreak included the first reported occurrence of Ebola virus disease in the RC.[25]
Occurred in Yambio county in Western Equatoria of southern Sudan (present-day South Sudan). This outbreak was concurrent with an outbreak of measles in the same area, and several suspected EVD cases were reclassified later as measles cases.[28]
This was the most severe Ebola outbreak in recorded history in regards to both the number of human cases and fatalities. It began in Guéckédou, Guinea, in December 2013 and spread abroad.[37][38][33] Flare-ups of the disease continued into 2016,[39] and the outbreak was declared over on 9 June 2016.
Occurred in Équateur province. Outbreak detected 24 August and, as of 28 October 2014, the WHO said that twenty days had passed since the last reported case was discharged and no new contacts were being followed.[40][41] Declared over on 15 November 2014.[42]
On 8 May 2018, the government of the Democratic Republic of the Congo reported two confirmed cases of Ebola infection in the northwestern town of Bikoro.[43] On 17 May, a case was confirmed in the city of Mbandaka.[44] Health authorities were planning to ring vaccinate with rVSV-ZEBOV, a recently developed experimental Ebola vaccine, to contain the outbreak.[44][45] The outbreak was ongoing as of 24 June 2018, in 2014 a different area of Equateur province was affected[46][47]
On 24 July 2018 the outbreak was declared over.[48][49][50][51]
On 1 August 2018, the Democratic Republic of the Congo Ministry of Health declared an outbreak when 4 individuals tested positive for the Ebola virus.[54][55][56][57] On 11 June 2019, the WHO confirmed that a five-year-old boy in Uganda died after being diagnosed with Ebola.[58][59] On 25 June 2020, the second biggest EVD outbreak ever was declared over.[60]
By 18 November 2020, the World Health Organization and the Congolese government had not received reports of any cases of Ebola in Équateur province or all of the DRC for 42 days.[65] When the outbreak was declared over, there were 130 reported cases and 55 reported fatalities due to the virus.[66]
First Ebola cases and deaths in the country since 2016.[67][69] The first cases were confirmed on 14 February 2021, and by 9 April 2021, there were 23 reported cases of the virus, with 12 fatalities and 9 recoveries.[70] Scientists concluded that the likely source of the outbreak was a man who had survived the 2013-2016 West African epidemic but had unknowingly harbored the Ebola virus in his body, eventually transmitting it to somebody in his community, although the first known case of this current outbreak was a female nurse who had died on 28 January 2021.[71] The outbreak was declared over on 19 June 2021.[72]
On 20 September 2022 an outbreak was declared in Mubende District, Uganda. Seventy-seven people died, with a total of 164 cases detected. The outbreak was declared over in January 2023.[75]
The Reston virus (RESTV) was first identified when it caused high mortality in crab-eating macaques in a primate research facility responsible for exporting animals to the United States.[80] Three workers in the facility developed antibodies to the virus but did not get sick.[81]
RESTV was introduced into quarantine facilities in Virginia and Pennsylvania by monkeys imported from the Philippines. No human cases were reported.[82]
Monkeys imported from the Philippines introduced RESTV into quarantine facilities in Virginia and Texas. Four humans developed antibodies but did not get sick.[83]
RESTV was introduced into quarantine facilities in Siena by monkeys imported from the same facility in the Philippines that was the source of the 1989 and 1990 U.S. outbreaks. No human cases resulted.[84]
This case was the first and thus far only recognition of Taï Forest virus (TAFV). Approximately one week after conducting necropsies on infected western chimpanzees in Taï National Park, a scientist contracted the virus and developed symptoms similar to those of dengue fever. She was discharged from a Swiss hospital two weeks later and fully recovered after six weeks.[85]
One person, fleeing the civil war in neighboring Liberia, was identified as an Ebola case in Gozon. This is considered as a suspected case, excluding from the WHO outbreak counts.[86][87]
RESTV was again introduced into a quarantine facility in Texas by monkeys imported from the same facility in the Philippines that was the source of the 1989 and 1990 U.S. outbreaks. No human cases resulted.[88]
First recognition of RESTV in pigs. Strain very similar to earlier strains. Occurred in November. Six workers from the pig farm and slaughterhouse developed antibodies but did not become sick.[92][93]
On 6 September 2015, the Philippine health secretary reported an outbreak of RESTV in a primate research and breeding facility. Twenty-five workers subsequently tested negative for the virus.[94]
In August 2021, two months after the re-emergent Ebola epidemic in the Guéckédou prefecture was declared over, a case of the Marburg virus disease was confirmed by health authorities through laboratory analysis.[106] This is the first-ever case of the Marburg virus disease in West Africa.[107] On August 2, the patient succumbed to the illness.[108]
^The case was repatriated to Switzerland for medical treatment.[85]
^ The mortality rate (death/case ratio) recorded in Liberia up to 26 August 2014 was 70 percent.[34] However, the general estimated case fatality rate (70.8 percent) for this ongoing epidemic differs from the ratio of the number of deaths divided by that of cases due to the estimation method used. Current infections have not run their course, and the estimate may be poor if reporting is biased towards severe cases.
^ The Centers for Disease Control chronology notes this infection as "Sudan virus", whereas the 1977 British Medical Journal (BMJ) article refers to it as "Ebola virus". In 1977, there was no distinction between different ebolaviruses. The BMJ article notes only that the patient received "convalescent serum from the Sudan" following similar serum from Zaire
References
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