Ebola epidemiology and demographics

Ebola Microchapters
Home
Patient Information
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Ebola from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
Algorithm for the Evaluation of the Returned Traveler
Emergency Department Evaluation
Case Definition
History and Symptoms
Physical Examination
Laboratory Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Hospital Preparedness
Checklists
Air Medical Transport
Monitoring and Movement Following Exposure
Primary Prevention
Future or Investigational Therapies
Postmortem Care
Postmortem Care
Case Studies
Case #1
Ebola epidemiology and demographics On the Web
Most recent articles
Most cited articles
Review articles
CME Programs
Powerpoint slides
Images
American Roentgen Ray Society Images of Ebola epidemiology and demographics All Images X-rays Echo & Ultrasound CT Images MRI
Ongoing Trials at Clinical Trials.gov
US National Guidelines Clearinghouse
NICE Guidance
FDA on Ebola epidemiology and demographics
CDC on Ebola epidemiology and demographics
Ebola epidemiology and demographics in the news
Blogs on Ebola epidemiology and demographics
Directions to Hospitals Treating ebola
Risk calculators and risk factors for Ebola epidemiology and demographics

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Michael Maddaleni, B.S.; Guillermo Rodriguez Nava, M.D. [2] Ahmed Younes M.B.B.CH [3] Syed Hassan A. Kazmi BSc, MD [4]

Overview

Outbreaks of Ebola have been generally restricted to Africa. Governments and individuals should quickly quarantine the area. Lack of roads and transportation help to contain the outbreak in remote areas. The potential for widespread Ebola virus disease epidemics is considered low due to the high case-fatality rate, the rapidity of the demise of patients, and the often remote areas where infections occur.

2020 Outbreak Updates

• On 31 May 2020, the World Health Organization (WHO) received information that between 18 and 30 May, 4 deaths were reported from Mbandaka Health Zone, Mbandaka city, Equateur Province, the Democratic Republic of the Congo.
• As of 2 June 2020, 8 cases, including 2 confirmed alive cases, 2 suspected cases and 4 deaths (1 confirmed and 3 probable deaths), have been reported. On June 1, 2020, the Ministry of Health (MOH) officially declared the outbreak in Equateur Province.
• This is the 11th outbreak of Ebola virus disease reported in the Democratic Republic of the Congo since the discovery of the virus in 1976.

2019 Outbreak Updates

On June 11, 2019, the Ministry of Health and the World Health Organization (WHO) confirmed a case of Ebola Virus Disease in Uganda. Although there have been numerous previous alerts, this is the first confirmed case in Uganda during the Ebola outbreak on-going in neighboring Democratic Republic of the Congo. A 5-year-old Congolese boy was diagnosed with the virus in Uganda. This is the 10th outbreak in Congo since 1976.

• An increase in the incidence of new cases has been reported from Mabalako Health Zone in recent weeks, and high infection rates continue within Butembo metropolitan. Times between detecting, reporting and admission of cases at Ebola treatment/transit centres (ETCs) remains too long (median 6 days, interquartile range 4–9 days in the past 3 weeks), with about a third (34% in the past 3 weeks) of cases dying outside of ETCs.
• In the 21 days between 15 May to 4 June 2019, 80 health areas within 12 health zones reported new cases, representing 12% of the 664 health areas within North Kivu and Ituri provinces. During this period, a total of 280 confirmed cases were reported, the majority of which were from the Mabalako (27%, n=75), Butembo (23%, n=63), Katwa (16%, n=44), Beni (11%, n=30), Kalunguta (8%, n=23), Mandima (7%, n=19) and Musienene (5%, n=14) health zones.
• As of 4 June 2019, a total of 2025 EVD cases, including 1931 confirmed and 94 probable cases, were reported. A total of 1357 deaths were reported (overall case fatality ratio 67%), including 1263 deaths among confirmed cases. Of the 2025 confirmed and probable cases with known age and sex, 58% (1170) were female, and 29% (589) were children aged less than 18 years. The number of healthcare workers affected has risen to 110 (5% of total cases).

Ebola Cases by Health Area, Courtesy: World Health Organization, June 4, 2019

2018 Outbreak Updates

In early May 2018, there was an outbreak of Ebola virus disease (EVD) in the Bikoro region of Equateur Province in the northwestern part of the Democratic Republic of Congo (DRC).  The DRC government declared the outbreak on May 8 after two cases were confirmed by laboratory testing at the Institut National de Recherche Biomédicale in Kinshasa.  CDC is assisting the DRC government and local and international partners, including the World Health Organization (WHO) to address the outbreak.

• On August 1, 2018, the Ministry of Health of the Democratic Republic of Congo reported an outbreak of Ebola Virus Disease in North Kivu Province. The current outbreak is located in the Mabalako, Beni, Oicha, and Mandima health zones of North Kivu and Ituri provinces. The area is about 780 miles away from Equateur province, where an Ebola outbreak was reported in May 2018. Although the ebolavirus species associated with the current outbreak is the same species that caused the earlier outbreak (Zaire ebolavirus), genetic differences between the viruses suggest the two outbreaks are not linked.
• This is the 10th Ebola outbreak in the Democratic Republic of Congo since the virus was discovered in 1976 in DRC.

Map of DR Congo Affected Regions

Adopted from WHO weekly bulletin on outbreaks and other emergencies on May 12, 2017

2017 Outbreak updates

Country	Date	Cases (confirmed and suspected)	Deaths	More details
The Democratic Republic of Congo (DRC)	May 12th, 2017	9	1 (11.1%)	In May 11th, 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
	May 14th, 2017	11	3 (27%)	The extent of the outbreak is not yet fully estimated but WHO recommends restriction of trade and travel with DRC. WHO's general director in Africa has met governmental representatives in Kinshasa to discuss measures to contain the outbreak.
	May 17th, 2017	11	3 (27%)	About 125 people of the contacts of the infected people are being monitored for possible development of the symptoms. Isolation facilities are being set up in case the outbreak involves wider areas.
	May 18th, 2017	18	3 (17%)	The number of contacts of infected people that are being followed and monitored for development of symptoms rises to 400. Personal Protective Equipment (PPE) for healthcare workers has been shipped to DR Congo. UNICEF workers have arrived and began aiding in setting up mobile laboratory sites in nearby regions. The Congolese government is in talks with the WHO in regards to "ring vaccination" of patient contacts with an experimental vaccine developed by an American company.
	May 19th, 2017	29	3 (10%)	416 contacts of infected patients are being followed.
	May 21st, 2017	32	4 (13%)	The reported cases are from five health areas: Nambwa, Muma, Ngayi, Azande, and Ngabatala
	May 22nd, 2017	34	4 (12%)	54 contacts completed daily contact monitoring and 362 remain under follow up with daily monitoring
	May 22nd, 2017	37	4 (11%)	Institut National de Recherche Biomedicale (INRB)) mobile laboratory began processing samples with 22 testing negative by PCR
	May 22nd, 2017	38	4 (11%)	33 samples have tested negative by PCR thus far 3 additional contacts were identified. 365 contacts remain under daily follow up for signs and symptoms of ebola.
	May 25th, 2017	43	4 (9%)	Experts estimate  that the 1400 Km isolation around Kinshasa has limited the spread of the disease. However, refugee flow across the borders towards the afflicted Bas-Uele region escaping the recent attacks of fighting militias puts the refugees at increased risk of infection and undermines the efforts to contain the outbreak.
	May 28th, 2017	43	4 (9%)	No new reported cases nor deaths 357 contacts are being monitored for symptoms and signs of ebola Based on the limited number of new confirmed cases, the risk is declared to be low with simulated scenarios predict no further cases in the following 30 days.
	May 30th, 2017	52	4 (7%)	Authorities in DRC approves the new  rVSV-ZEBOV vaccine.
	June 3rd, 2017	52	4 (7%)	No new confirmed cases .. with the last confirmed case was on May 22nd 2017 All the contacts of confirmed cases completed the follow up period of 21 days and none of them developed the symptoms of ebola. The risk remains low but not negligible.
	July 2nd, 2017	8 (confirmed cases)	4 (50%)	On July 2nd 2017, WHO declared that the recent outbreak has come to an end. This comes after 42 days of follow up of the contacts of the last diagnosed case (representing 2 incubation cycles of the virus). In total, 8 cases were confirmed to have ebola, 4 of them died. Only 5 of the 8 cases were laboratory confirmed. For these 8 cases, there were 583 contacts that have been closely monitored. None of the contacts developed the symptoms of ebola. The DRC government success to control the outbreak is thought to be due to: Reporting the cases by local authorities in the proper time before further spread of the disease. Testing blood samples and confirming the disease in a timely fashion (due to augmented lab facilities after the last outbreak) Announcing the outbreak early by the government, which allowed early response by the WHO. Survivors of the outbreak still have access to medical facilities allowing screening for persistent virus. {{#ev:youtube|tNZi8MLsMWM}}

Map of DR Congo Affected Regions

Adopted from WHO weekly bulletin on outbreaks and other emergencies on May 12, 2017

2014 Outbreak

The first reported case of the recent outbreak was diagnosed in Guinea in December 2013. From there it spread to Liberia, Sierra Leone, Nigeria, and Senegal. The first case in the United States was confirmed on September 30, 2014.

Country	Case definition	Cases	Deaths
Guinea	Confirmed	2762	1704
	Probable	387	387
	Suspected	6	-
	All	3155	2091
Liberia	Confirmed	3153	-
	Probable	1888	-
	Suspected	4197	-
	All	9238	4037
Sierra Leone	Confirmed	8289	3095
	Probable	287	208
	Suspected	2725	158
	All	11,301	3461
Nigeria	Confirmed	19	7
	Probable	1	1
	Suspected	0	0
	All	20	8
Senegal	Confirmed	1	0
	Probable	0	0
	Suspected	0	0
	All	1	0
United States	Confirmed	3	1
	Probable	0	0
	Suspected	0	0
	All	3	1
Spain	Confirmed	1	0
	Probable	0	0
	Suspected	0	0
	All	1	0
Total		23,719	9,598

As of February 25, 2015. Data from the World Health Organization

Cases of Ebola in Africa

Cases of Ebola Hemorrhagic Fever in Africa, 1976 - 2017 Country Town Cases Deaths Species Year Dem. Rep. of Congo Yambuku 318 280 Zaire ebolavirus 1976 South Sudan Nzara 284 151 Sudan ebolavirus 1976 Dem. Rep. of Congo Tandala 1 1 Zaire ebolavirus 1977 South Sudan Nzara 34 22 Sudan ebolavirus 1979 Gabon Mekouka 52 31 Zaire ebolavirus 1994 Ivory Coast Tai Forest 1 0 Taï Forest ebolavirus 1994 Dem. Rep. of Congo Kikwit 315 250 Zaire ebolavirus 1995 Gabon Mayibout 37 21 Zaire ebolavirus 1996 Gabon Booue 60 45 Zaire ebolavirus 1996 South Africa Johannesburg 2 1 Zaire ebolavirus 1996 Uganda Gulu 425 224 Zaire ebolavirus 2000 Gabon Libreville 65 53 Zaire ebolavirus 2001 Republic of Congo Not specified 57 43 Zaire ebolavirus 2001 Republic of Congo Mbomo 143 128 Zaire ebolavirus 2002 Republic of Congo Mbomo 35 29 Zaire ebolavirus 2003 South Sudan Yambio 17 7 Zaire ebolavirus 2004 Dem. Rep. of Congo Luebo 264 187 Zaire ebolavirus 2007 Uganda Bundibugyo 149 37 Bundibugyo ebolavirus 2007 Dem. Rep. of Congo Luebo 32 15 Zaire ebolavirus 2008 Uganda Luwero District 1 1 Sudan ebolavirus 2011 Uganda Kibaale District 11* 4* Sudan ebolavirus 2012 Dem. Rep. of Congo Isiro Health Zone 36* 13* Bundibugyo ebolavirus 2012 Uganda Luwero District 6* 3* Sudan ebolavirus 2012 Guinea, Sierra Leone, Liberia multiple 7470 3431 Zaire ebolavirus 2014 Dem. Rep. of Congo multiple 70 43 Zaire ebolavirus 2014 Dem. Rep. of Congo Bas-Uele 38 4 Zaire ebolavirus 2017

Ebola Hemorrhagic Fever Distribution Map. Adapted from Centers for Disease Control and Prevention

Major Historical Outbreaks

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

Year(s)	Country	Ebola subtype	Reported number of human cases	Reported number (%) of deaths among cases	Situation
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.

West Africa outbreak (2013-2014)

First affected Districts in Guinea and neighboring areas.
Image extracted from WHO: Ebola Hemorrhagic Fever in Guinea

Distribution of confirmed and suspected cases as of 16 June 2014.
Image extracted from WHO: Ebola Virus Disease (EVD) in West Africa (situation as of 16 June 2014)

On March 23, 2014, the Ministry of Health of Guinea notified the World Health Organization (WHO) of a rapidly evolving outbreak of Ebola virus disease (EVD) in forested areas south eastern Guinea: Guekedou, Macenta, Nzerekore and Kissidougou districts. As of 22 March 2014, a total of 49 cases including 29 deaths (case fatality ratio: 59%) were reported. Four health care workers were among the victims. At the same time, suspected cases in border areas of Liberia and Sierra Leone were being investigated. Six blood samples were tested at Institut Pasteur in Lyon, France, resulting positive for Ebola virus by PCR, confirming the first Ebola virus disease outbreak in Guinea. Preliminary results from sequencing of a part of the L gene showed strong homology with Zaire Ebolavirus. The ministry of health together with the WHO and other partners initiated measures to control the outbreak and prevent further spread. Médecins Sans Frontières, Switzerland (MSF-CH) started working in the affected areas and assisted with the establishment of isolation facilities, and also supported transport of the biological samples from suspected cases and contacts to international reference laboratories for urgent testing. The Emerging and Dangerous Pathogens Laboratory Network (EDPLN) worked with the Guinean VHF Laboratory in Donka, the Institut Pasteur in Lyon, the Institut Pasteur in Dakar, and the Kenema Lassa fever laboratory in Sierra Leone to make available appropriate Filovirus diagnostic capacity in Guinea and Sierra Leone.

On 30 March, 2014, the Ministry of Health of Liberia provided updated details on the suspected and confirmed cases of Ebola virus disease in Liberia. As of 29 March, seven clinical samples, all from adult patients from Foya District, Lofa County, were tested by PCR using Ebola Zaire virus primers by the mobile laboratory of the Institut Pasteur (IP) Dakar in Conakry. Two of those samples tested positive for the ebolavirus. There were 2 deaths among the suspected cases; a 35-year-old woman who died on 21 March tested positive for ebolavirus while a male patient who died on 27 March tested negative. At that time, Foya was the only district in Liberia that reported confirmed or suspected cases of Ebola Hemorrhagic Fever. As of 26 March, Liberia had 27 contacts under medical follow-up. Liberia established a high-level National Task Force to lead the response. Response partners include WHO, the International Red Cross (IRC), Samaritan’s Purse (SP) Liberia, Pentecostal Mission Unlimited (PMU)-Liberia, CHF-WASH Liberia, PLAN-Liberia, UNFPA and UNICEF.

On 3 April, 2014, the outbreak was confirmed to be caused by a strain of ebolavirus with very close homology (98%) to the Zaire ebolavirus. This is the first time the disease has been detected in West Africa.

Democratic Republic of the Congo (2007)

As of August 30, 2007, 103 people (100 adults and three children) were infected by a suspected hemorrhagic fever outbreak in the village of Mweka, Democratic Republic of the Congo (DRC). The outbreak started after the funerals of two village chiefs, and 217 people in four villages fell ill. The World Health Organization sent a team to take blood samples for analysis and confirmed that many of the cases are the result of the Ebola virus . The Congo's last major Ebola epidemic killed 245 people in 1995 inKikwit, about 200 miles from the source of the Aug. 2007 outbreak.

On November 30, 2007, the Uganda Ministry of Health confirmed an outbreak of Ebola in the Bundibugyo District. After confirmation of samples tested by the United States National Reference Laboratories and the Centers for Disease Control, the World Health Organization confirmed the presence of a new species of the Ebola virus. The epidemic came to an official end on February 20, 2008. 149 cases of this new strain were reported and 37 of those led to deaths.

Uganda Outbreak (2000)

On October 8, 2000, an outbreak of an unusual febrile illness with occasional hemorrhage and significant mortality was reported to the Ministry of Health (MoH) in Kampala by the superintendent of St. Mary's Hospital in Lacor, and the District Director of Health Services in the Gulu District. A preliminary assessment conducted by MoH found additional cases in Gulu District and in Gulu Hospital, the regional referral hospital. On October 15, suspicion of Ebola hemorrhagic fever (EHF) was confirmed when the National Institute of Virology (NIV), Johannesburg, South Africa, identified Ebola virus infection among specimens from patients, including health-care workers at St. Mary's Hospital. This report describes surveillance and control activities related to the EHF outbreak and presents preliminary clinical and epidemiologic findings.

Control activities were organized around surveillance and epidemiology, clinical case management, social education and mobilization, and coordination and logistic support. An active EHF surveillance system was initiated to determine the extent and magnitude of the outbreak, identify foci of disease activity, and detect cases early. Ill persons were encouraged to be assessed at a hospital and, if indicated, to be hospitalized to reduce further community transmission. Targeted prevention activities included follow-up of contacts of identified cases for 21 days; establishment of trained burial teams for all potential and confirmed EHF deaths; community education; cessation of traditional healing and burial practices; cessation of large public gatherings; and updates of hospital infection-control measures, including isolation wards. Laboratory testing was performed at a field laboratory established at St. Mary's Hospital by CDC and supplemented by additional testing at CDC and NIV. Sequence analysis revealed that the virus associated with this outbreak was Ebola-Sudan and differed at the nucleotide sequence level from earlier Ebola-Sudan isolates by 3.3% and 4.2% in the polymerase (362 nucleotides sequenced) and nucleocapsid (146 nucleotides sequenced) protein encoding genes, respectively.

During the third week of October, active surveillance was established and included three case notification categories: alert, suspect, and probable. The alert category comprised persons with sudden onset of high fever, sudden death, or hemorrhage, and was used by community members to alert health-care personnel. The suspect category comprised persons with fever and contact with a potential case-patient; persons with unexplained bleeding; persons with fever and three or more specified symptoms (i.e., headache, vomiting, anorexia, diarrhea, weakness or severe fatigue, abdominal pain, body aches or joint pains, difficulty swallowing, difficulty breathing, and hiccups), and all unexplained deaths. The suspect category was used by mobile surveillance teams to determine whether a patient required transport to an isolation ward. The probable category included persons who met these criteria and were assessed and reported by a physician. Laboratory tests included virus antigen detection and antibody ELISA tests and reverse transcriptase polymerase chain reaction. Laboratory-confirmed case-patients were defined as patients who met the surveillance case definitions and were either positive for Ebola virus antigen or Ebola IgG antibody.

During October 5--November 27, among 62 persons with laboratory-confirmed EHF admitted to Gulu Hospital, symptoms included diarrhea (66%), asthenia(64%),anorexia (61%), headache (63%), nausea and vomiting (60%), abdominal pain (55%), and chest pain (48%). Patients presented for care a mean of 8 days (range: 2--20 days) after symptom onset. Bleeding occurred in 12 (20%) patients and primarily involved the gastrointestinal tract. Among the 62 confirmed case-patients, 36 (58%) died; among patients aged <15 years, four of five died (case fatality: 80%). Spontaneous abortions were reported among pregnant women infected with EHF. Patients who died usually exhibited a rapid progression of shock, increasing coagulopathy, and loss ofconsciousness.

As of January 23, 2001, 425 presumptive* case-patients with 224 (53%) deaths attributed to EHF were recorded from three districts in Uganda: 393 (93%) from Gulu, 27 (6%) from Masindi, and five (1%) from Mbarara. The combined area comprises approximately 11,700 square miles (31,000 square kilometers; 2000 combined population: 1.8 million) (See the map of Uganda below) (1). Although the cluster of cases in early October triggered identification of the outbreak and response measures, investigations (i.e., case-record review and interviews with surviving patients or their surrogates) identified cases occurring in the community and patients hospitalized several weeks earlier. The onset of illness of the earliest presumptive case was August 30, 2000, and onset of last presumptive case was January 9, 2001 (See the graph below the map of Uganda). The ages of presumptive case-patients ranged from 3 days--72 years (median: 28 years); 269 (63%) were women. Mean time from symptom onset to death was 8 days (95% confidence interval=±5 days); 218 (51%) presumptive cases were laboratory confirmed.

Epidemiologic investigations identified the three most important means of transmission as attending funerals of presumptive EHF case-patients where ritual contact with the deceased occurred, and intrafamilial or nosocomial transmission. Fourteen (64%) of 22 health-care workers in Gulu were infected after establishing the isolation wards; these incidences led to the reinforcement of infection-control measures. Two distant focal outbreaks were initiated by movement of infected contacts of EHF cases from Gulu to Mbarara and Masindi districts. National notification and surveillance efforts led to the rapid identification of these foci and effective containment.

Distribution of presumptive case-patients with Ebola hemorrhagic fever-Uganda August 2000-January 2001Adapted from Centers for Disease Control and Prevention.

Number of presumptive case-patients with Ebola hemorrhagic fever, by week of onset - Uganda, August 2000-January 2001Adapted from Centers for Disease Control and Prevention.