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. 2015 May 26;2:150019. doi: 10.1038/sdata.2015.19

Table 6. Parameter estimates for the ongoing outbreak in West Africa.

Parameter All countries * Guinea Liberia Nigeria Sierra Leone References
Rt refers to effective reproduction number.
            
μ=mean; Med=median; s.d.=standard deviation.
            
WHO ERT is the World Health Organization Ebola Response Team16,17.
            
Incubation Period Distribution (days)
           
 Multi-day exposures, observed (mean) 11.4, n=155 10.9, n=20 11.7, n=79 — 10.8, n=48 16
 Single-day exposures, observed, (median (IQR)) 9 (5–13) 17
 Fitted single-day exposures (mean, (95% CI)) 10.3 (9.9, 10.7) 17
 Fitted values (mean) 12 10 48
Serial interval Distribution (days)
           
 WHO ERT 2014 (gamma fit mean, s.d., n) 15.3, 9.3, n=92) 19.0, 11.2, n=40) 13.1, 7.8, n=26) — 11.6, 6.3, n=25) 16
 WHO ERT 2015 (gamma fit mean, (95% CI), n) 14.2 (13.1, 15.3), n=305 17
 Fisman et al. 30 15 days (derived) 30
 Faye et al. 2014 (mean, (range), s.d., (95% CI for s.d.)) 14.2 (13.1–15.5), 7.1 (6.2, 8.2) 41
R0 (estimate, (95% CI))
           
 With estimated serial interval 15.3 d — 1.71 (1.44, 2.01) 1.83 (1.72, 1.94) 2.02 (1.79, 2.26) 16
 With fixed incubation period 5.3 d — 1.51 (1.50, 1.52) 1.59 (1.57, 1.60) 9.0 (5.2, 15.6) † 2.53 (2.41, 2.67) 36,61
 Overall, data driven 1.8 (1.5, 2.0) — — — — 62
 SEIR model 2.1 (1.9, 2.4) — — — — 62
 Community using Legrand et al. 59 model 0.8 (0.3, 0.9) — — — — 62
 Hospital using Legrand et al. 59 model 0.4 (0.2, 1.4) — — — — 62
 Funeral using Legrand et al. 59 model 0.6 (0.2, 1.0) — — — — 62
 Assumed fixed generation time of 15d 1.78 2.46 1.72 — 8.33 30
 Estimated mean serial interval 15.3d — 1.71 (1.44, 2.01) 1.83 (1.72, 1.94) 1.2 (0.67, 1.96) 2.02 (1.79, 2.26) 16
 Overall (Conakry) 1.7 (1.2, 2.3) 41
 Community (Conakry) 1.0 (0.6, 1.5) 41
 Hospital (Conakry) 0.4 (0.2, 0.7) 41
 Funeral (Conakry) 0.3 (0.1, 0.6) 41
 Montserrado only 2.49 (2.38, 2.60) 64
 Webb et al. 2015 1.54 1.26 68
 Rivers et al. 48 (overall) 2.22 1.78 48
 Rivers et al. 48 (community) 1,35 1.11 48
 Rivers et al. 48 (hospitals) 0.35 0.24 48
 Rivers et al. 48 (funerals) 0.53 0.43 48
 Khan et al. 63 (raw data) 1.76 1.49 63
 Khan et al. 63 (corrected for underreporting) 1.9 1.37 63
Rt (estimate, (95% CI))
           
 Estimated mean serial interval 15.3 d — 1.81 (1.60, 2.03) 1.51 (1.41, 1.60) <1† 1.38 (1.27, 1.51) 16,36
 Estimated mean generation time 12 d‡ — 1 1.7 — 1.4 65
 Sierra Leone (56 days of data) 1.1 (0.95, 1.24) 69
 Montserrado only 1.73 (1.66, 1.83) 76
 Survivors Montserrado only 0.66 (0.10, 1.69) 76
 Non-survivors Montserrado only 2.36 (1.72, 2.80) 76
Observed Delay Distributions (days)
           
 Symptom onset to…
           
  … hospitalization
           
   WHO ERT 2014 (mean, s.d., n) 5.0, 4.7, n=1135 5.3, 4.3, n=484 4.9, 5.1, n=245 4.1, 1.4, n=11 4.6, 5.1, n=395 16
   WHO ERT 2015 (mean, (95% CI), n) 5.0 (4.9, 5.1), n=5616 17
   Faye et al. 2014 (mean, s.d., n) 5.0, 3.9, n=152
   Rivers et al. 48 (mean) 3.24 4.12 48
  ... hospital discharge
           
   WHO ERT 2014 (mean, s.d., n) 16.4, 6.5, n=267 16.3, 6.1, n=152 15.4, 8.2, n=41 — 17.2, 6.2, n=70 16
   WHO ERT 2015 (mean, (95% CI)) 15.1 (14.6, 15.6) 17
  … death
           
   WHO ERT 2014 (mean, s.d., n) 7.5, 6.8, n=594 6.4, 5.3, n=248 7.9, 8, n=212 — 8.6, 6.9, n=128 16
   WHO ERT 2015 (mean, (95% CI)) 8.2 (7.9, 8.4) 17
   Faye et al. 2014 (mean, s.d., n) 8.9, 4.0, n=82) 41
   Althaus et al. 61 (mean, range) 7.41 (4–17), n=17 61
  … WHO notification 6.1, 8.5, n=2185 7.5, 10.4, n=743 6, 8.7, n=797 — 4.5, 5, n=634 16
WHO notification to…
           
 … hospital discharge (mean, s.d., n) 11.8, 7.2, n=312 11.1, 5.8, n=164 11, 8, n=41 — 12.7, 8.4, n=102 16
  … death (mean, s.d., n) -3.0, 13.8, n=584 -4.4, 14.4, n=300 -1.8, 13.6, n=221 — -1.6, 9.2, n=58 16
Hospitalization to…
           
 … discharge
           
  WHO ERT 2014 (mean, s.d., n) 11.8, 6.1, n=290 11, 5.4, n=159 12.8, 8.1, n=40 — 12.4, 5.8, n=86 16
  WHO ERT 2015 (mean, (95% CI)) 11.2 (10.8, 11.7) 17
  Rivers et al. 48 (recovery) (mean) 15.88 15.88 48
 … death
           
  WHO ERT 2014 (mean, s.d., n) 4.2, 6.4, n=121 2.5, 3.4, n=36 4.5, 6, n=63 — 4.4, 6, n=17 16
  WHO ERT 2015 (mean, (95% CI)) 4.3 (4.1, 4.5) 17
  Rivers et al. 48 (mean) 10.07 6.26 48
Infectious period
           
 Rivers et al. 48 (mean) 15.00 18.00 48
Infection to death
           
 Rivers et al. 48 (mean) 13.31 10.38 48
Case Fatality Rate (estimate, (95% CI), n)
           
 WHO ERT 2014 (based on current status) 37.7 (36.1, 39.2), n=3747 57.5 (53.7, 61.1), n=677 34.7 (32.4, 37.1), n=1616 40.0 (19.8–64.3), n=15 31.6 (29.3, 34.1), n=1439 16
 Althaus 36 (based on reported deaths) 74 (72, 75), n=607 71 (69, 74), n=1082 48 (47, 50), n=910 36
All cases (based on definitive outcome)
           
 WHO ERT 2014 70.8 (68.6, 72.8), n=1737 70.7 (66.7, 74.3), n=542 72.3 (68.9, 75.4), n=739 45.5 (21.3, 72), n=11 69.0 (64.5, 73.1), n=445 16
 WHO ERT 2015 70.4 (69.2, 71.6), n=5616 17
 Althaus et al. 61 39 (14, 71), n=20 61
 Fasina et al. 54 40 (22, 61), n=20 54
All hospitalized cases
           
 WHO ERT 2014 (based on definitive outcome) 63.5 (60.5, 66.3), n=1100 63.4 (58.6, 67.9), n=434 66.6 (61.3, 71.6), n=338 100 (2.5, 100), n=1 61 (55.4, 66.4), n=318 16
 WHO ERT 2015 (based on definitive outcome) 60.7 (59.2, 62.3), n=3839 17
 Rivers et al. 48 0.500 0.750 48
Subset of Cases
           
 Faye et al. 2014 (Conakry) 54 (49, 63), n=152 41

*here all countries refer to Guinea, Liberia and Sierra Leone.

†R0 of the index case arriving by air travel from Liberia; Rt estimated to be below 1 within 15 days (95% CI 11–21 days) after arrival of the index case from Liberia36

‡Authors refer to generation time, but have estimated the serial interval and assumed serial interval is the same as generation time.