1. Epidemiology and Global Health
Download icon

Ebola virus disease in the Democratic Republic of the Congo, 1976-2014

  1. Alicia Rosello  Is a corresponding author
  2. Mathias Mossoko
  3. Stefan Flasche
  4. Albert Jan Van Hoek
  5. Placide Mbala
  6. Anton Camacho
  7. Sebastian Funk
  8. Adam Kucharski
  9. Benoit Kebela Ilunga
  10. W John Edmunds
  11. Peter Piot
  12. Marc Baguelin  Is a corresponding author
  13. Jean-Jacques Muyembe Tamfum
  1. Public Health England, United Kingdom
  2. University College London, United Kingdom
  3. Direction de lutte contre la maladie, Democratic Republic of the Congo
  4. London School of Hygiene and Tropical Medicine, United Kingdom
  5. Institut National de Recherche Biomédicale, Democratic Republic of the Congo
Research Article
Cite this article as: eLife 2015;4:e09015 doi: 10.7554/eLife.09015
Voice your concerns about research culture and research communication: Have your say in our 7th annual survey.
7 figures, 5 tables and 2 additional files

Figures

Map and historical timeline of the EVD outbreaks in the DRC.

(A) Map of the Democratic Republic of the Congo (DRC) where the area of the circles are proportional to the number of cases (probable and confirmed) per outbreak. (B) The outbreaks (in orange) and relevant wars (in purple) are positioned in time.

https://doi.org/10.7554/eLife.09015.003
Incidence of cases by age and sex in the DRC outbreaks in comparison to the demographics of the national 1975–2010 population.
https://doi.org/10.7554/eLife.09015.006
Time course of the EVD outbreaks in DRC.

Confirmed cases are plotted in red, probable cases in orange, suspected in light blue, cases that were either suspected or probable cases in dark blue, and cases for whom the definition was unknown in purple. The dashed lines represent important events that occurred during the outbreaks (in orange, the first records of the disease, in red, the first notifications, and in black, important interventions carried out). For Yambuku, this was the closure of Yambuku Mission Hospital; for Kikwit, the closure of all hospitals, health centres, and laboratories in the area; for Mweka 2007, the opening of two mobile laboratories; for Mweka 2008, the opening of the first isolation centre; for Isiro, first the opening of the isolation centre and later the opening of the laboratory; and for Boende, the opening of the first isolation centre. Notification dates were when the cases were first notified to the Direction de Lutte contre la Maladie (DLM).

https://doi.org/10.7554/eLife.09015.007
Percentage of probable and confirmed cases with abdominal pain, diarrhoea, fever, haemorrhagic symptoms, headache, and vomiting.

These were calculated by dividing the number of probable and confirmed cases with symptoms by the number of probable and confirmed cases with symptoms, no symptoms, and blanks for cases for who the presence or absence of at least one symptom was reported. Note that the majority of cases in the Mweka 2007 outbreak were diagnosed a posteriori using recorded symptoms.

https://doi.org/10.7554/eLife.09015.008
Figure 5 with 2 supplements
Evolving case-fatality ratios with time after the start of the outbreak.

Monthly point estimates are presented with 95% binomial confidence intervals. The dashed horizontal line indicates the average case-fatality ratio (CFR) during each outbreak. The vertical dashed lines represent important events that occurred during the outbreaks (in red, the first notifications, and in black, important interventions carried out). For Yambuku, this was the closure of Yambuku Mission Hospital; for Kikwit, the closure of all hospitals, health centres, and laboratories; for Mweka 2007, the opening of two mobile laboratories; for Mweka 2008, the opening of the first isolation centre; for Isiro, first the opening of the isolation centre and later the opening of the laboratory; and for Boende, the opening of the first isolation centre. Notification dates were when the cases were first notified to the DLM.

https://doi.org/10.7554/eLife.09015.009
Figure 5—figure supplement 1
CFR by age groups for each outbreak.
https://doi.org/10.7554/eLife.09015.010
Figure 5—figure supplement 2
Aggregated CFRs for all outbreaks by age group.
https://doi.org/10.7554/eLife.09015.011
Evolving effective reproduction numbers with time after the start of the outbreak and adjusted weekly incidence.

Weekly point estimates of the effective reproduction numbers are presented with 95% confidence intervals. The dashed horizontal line indicates the threshold R = 1. The vertical dashed lines represent important events that occurred during the outbreaks (in red, the first notifications, and in black, important interventions carried out). For Yambuku, this was the closure of Yambuku Mission Hospital; for Kikwit, the closure of all hospitals, health centres, and laboratories; for Mweka 2007, the opening of two mobile laboratories; for Mweka 2008, the opening of the first isolation centre; for Isiro, first the opening of the isolation centre and later the opening of the laboratory; and for Boende, the opening of the first isolation centre. The light grey bars represent the weekly incidence of Ebola virus disease (EVD) (omitting suspected cases) rescaled by dividing by seven.

https://doi.org/10.7554/eLife.09015.014
Delay distributions for the EVD outbreaks in the DRC.

The bars represent the observed frequency distributions of the delay from onset of symptoms to notification, onset of symptoms to hospitalisation, onset of symptoms to death, length of hospitalisation, and date of hospitalisation to death. Delays were censored at 30 days. The red line represents the respective fit of a gamma distribution.

https://doi.org/10.7554/eLife.09015.015

Tables

Table 1

Main characteristics of the outbreaks

https://doi.org/10.7554/eLife.09015.004
YambukuTandalaKikwitMweka 07Mweka 08/09IsiroBoende
EcosystemTropical rain forestRainforest/savannahUrban/peri-urbanForested savannahForested savannahTropical area of savannah scattered with gallery forestsTropical rainforest
InhabitantsSmall villages <500 residentsSmall villageVillages and city of 200,000170,000170,000700,000 exposed250,000 in Boende but most cases living in small villages
StartAug-76Jun-76Jan-95Apr-07Nov-08Jun-12Aug-12
EndOct-76Jun-76Jun-95Oct-07Jan-09Nov-12Oct-12
Healthcare facility involved in historyYambuku Catholic Mission HospitalKikwit II Maternity Unit and Kikwit General HospitalKaluamba health centre, injections clandestine nurse from KaluambaChemin de Fer des Uélé clinic (Isiro), Isiro General Reference HospitalAntenatal care in her village, Miracle centre in Isaka, Lokolia health centre
Index case detected?NoNoPossible: charcoal maker who worked in the forestNoNoNoNo
Table 2

Distribution of cases and deaths by type and overall case-fatality ratios per outbreak

https://doi.org/10.7554/eLife.09015.005
Yambuku (1976)Kikwit (1995)Mweka (2007)Mweka (2008/9)Isiro (2012)Boende (2014)All outbreaks
Cases (n)
 Suspected022
 Probable317221628383
 Confirmed24103638108
 Total318*317264325268733
Deaths (n)
 Suspected000
 Probable12152855
 Confirmed172132153
 Total280*248187142849526
Case-fatality ratio
 (%, 95% CI)88*78 (73–83)74 (68–79)44 (26–62)54 (39–68)74 (62–84)79 (76–82)
Sex
 (% Female, 95% CI)59 (53–65)54 (48–59)55 (48–61)72 (53–86)77 (63–87)53 (40–65)57 (54–60)
  1. Where the distinction between probable, confirmed, and suspected cases was available, the case-fatality ratio and % female were calculated with only probable and confirmed cases. Only cases for which outcomes were reported were included in the case-fatality ratio denominator.

  2. *

    The values presented in this table for Yambuku were taken from the literature, as our data are a subset of the total cases during the outbreak (262/318).

Table 3

Odds of dying from EVD

https://doi.org/10.7554/eLife.09015.012
OR2.50%97.50%
Outbreak Isiro 20120.890.312.59
Outbreak Kikwit 19955.441.4321.87
Age [0, 5)1.120.236.63
Age [5, 15)0.20.050.7
Months since first case0.690.480.97
Delay onset to hospitalisation1.111.021.21
  1. EVD, Ebola virus disease.

  2. Estimated through binomial regression with age group and year of outbreak as factorial covariates and the number of months since the start of the outbreak and the delay from symptom onset to hospitalisation as continuous covariates.

Table 4

Odds of dying from EVD

https://doi.org/10.7554/eLife.09015.013
CovariatesOR2.50%97.50%
Outbreak Isiro 20120.670.291.55
Outbreak Kikwit 19954.631.9610.94
Outbreak Mweka 20073.831.619.18
Outbreak Mweka 20080.250.10.63
Outbreak Yambuku 19767.113.1316.75
Age [0, 5)2.491.126.34
Age [5, 15)0.360.210.63
Months since first case0.650.540.77
  1. EVD, Ebola virus disease.

  2. Estimated through binomial regression with age group and year of outbreak as factorial covariates and the number of months since the start of the outbreak as continuous covariate.

Table 5

Mean values and standard deviations corresponding to the delay distributions

https://doi.org/10.7554/eLife.09015.016
OutbreakDelayMeanSD
1995 KikwitOnset to notification12.917.72
1995 KikwitOnset to hospitalisation5.023.91
1995 KikwitOnset to death9.474.44
1995 KikwitLength of hospital stay5.725.67
1995 KikwitHospitalisation to death4.53.69
2007 MwekaOnset to notification00
2008 MwekaOnset to notification10.048.47
2008 MwekaOnset to hospitalisation00
2008 MwekaOnset to death7.624.44
2008 MwekaLength of hospital stay1.52.12
2008 MwekaHospitalisation to death119.85
2012 IsiroOnset to notification8.838.29
2012 IsiroOnset to hospitalisation43.27
2012 IsiroOnset to death11.375.41
2012 IsiroLength of hospital stay86.56
2012 IsiroHospitalisation to death7.595.52
2014 BoendeOnset to notification6.235.08
2014 BoendeOnset to hospitalisation4.953.32
2014 BoendeOnset to death9.395.67
2014 BoendeHospitalisation to death4.864.23
  1. Delays distributions (delay from onset of symptoms to notification, onset of symptoms to hospitalisation, onset of symptoms to death, length of hospitalisation and date of hospitalisation to death).

Additional files

Supplementary file 1

Aggregated line list for all outbreaks in the Democratic Republic of the Congo.

https://doi.org/10.7554/eLife.09015.017
Supplementary file 2

Repository of the interventions carried out during all outbreaks in the Democratic Republic of the Congo.

https://doi.org/10.7554/eLife.09015.018

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Download citations (links to download the citations from this article in formats compatible with various reference manager tools)

Open citations (links to open the citations from this article in various online reference manager services)