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Volume 22, Number 8—August 2016
Research

Exposure-Specific and Age-Specific Attack Rates for Ebola Virus Disease in Ebola-Affected Households, Sierra Leone

Hilary Bower, Sembia Johnson, Mohamed S. Bangura, Alie Joshua Kamara, Osman Kamara, Saidu H. Mansaray, Daniel Sesay, Cecilia Turay, Francesco Checchi, and Judith R. GlynnComments to Author 
Author affiliations: London School of Hygiene & Tropical Medicine, London, UK (H. Bower, J.R. Glynn); Save the Children, Freetown, Sierra Leone (S. Johnson, M.S. Bangura, A.J. Kamara, O. Kamara, S.H. Mansaray, D. Sesay, C. Turay); Save the Children, London (F. Checchi)

Main Article

Table 4

Risk factors associated with development of EVD in subsequent case-patients in Ebola-affected households, Kerry Town, Sierra Leone, 2014–2015*

Risk factor No. patients/no. total (%),† N = 809 Adjusted RR‡
(95% CI) Adjusted RR§ (95% CI) Multivariable
RR¶ (95%CI) p value#
Sex
M 136/337 (40.4) 1.1 (0.87–1.4) 1.06 (0.85–1.3) 1.03 (0.87–1.2)
F
211/472 (44.7)
1
1
1
0.7
Age, y
<2 22/51 (43.1) 0.79 (0.49–1.3) 0.80 (0.49–1.3) 0.92 (0.64–1.3)
2–4 31/81 (38.3) 0.70 (0.45–1.1) 0.70 (0.46–1.1) 0.97 (0.72–1.3)
5–9 38/127 (29.9) 0.44 (0.28–0.68) 0.44 (0.28–0.69) 0.70 (0.50–0.97)
10–14 34/114 (29.8) 0.41 (0.25–0.67) 0.41 (0.25–0.67) 0.64 (0.45–0.93)
15–19 35/95 (36.8) 0.53 (0.33–0.84) 0.53 (0.33–0.84) 0.71 (0.49–1.02)
20–29 72/155 (46.5) 1 1 1
30–39 51/85 (60.0) 1.2 (0.82–1.6) 1.2 (0.82–1.6) 1.1 (0.83–1.4)
40–49 30/46 (65.2) 1.2 (0.82–1.8) 1.2 (0.83–1.8) 1.1 (0.80–1.6)
>50
33/53 (62.3)
1.3 (0.87–1.8)
1.3 (0.88–1.8)
1.3 (0.97–1.8)
0.004
Maximum exposure
Handled corpse 60/72 (83.3) 18.1 (7.4–44.1) 13.5 (5.4–33.5) 11.1 (4.5–27.4)
Handled fluids 73/120 (60.8) 13.1 (5.4–31.9) 9.7 (3.9–24.1) 8.5 (3.5–20.6)
Direct wet contact 146/297 (49.2) 10.4 (4.3–25.1) 8.3 (3.4–20.1) 7.1 (3.0–17.1)
Direct dry contact 47/125 (37.6) 7.1 (2.9–17.7) 5.6 (2.3–13.9) 5.3 (2.2–12.9)
Indirect wet contact 5/19 (26.3) 5.7 (1.6–20.1) 4.9 (1.4–16.8) 4.7 (1.5–14.6)
Indirect dry contact 8/74 (10.8) 1.4 (0.43–4.6) 1.3 (0.40–4.2) 1.3 (0.41– 4.0)
Minimal/no contact**
8/102 (7.8)
1
1
1
<0.001
Position in household
Household head 24/52 (46.2) 1.2 (0.79–1.79) 0.62 (0.35–1.1) 0.62 (0.39–1.0)
Household member
323/757 (42.7)
1
1
1
0.03
Household size
>16 120/209 (57.4) 5.2 (1.6–16.9) 5.0 (1.5–16.8) 2.9 (1.1–7.8)
11–15 98/290 (33.8) 2.4 (0.70–7.9) 2.4 (0.70–8.3) 1.7 (0.63–4.6)
6–10 121/270 (44.8) 3.7 (1.2–12.0) 3.9 (1.2–12.8) 2.7 (1.04–7.0)
1–5
8/40 (20.0)
1
1
1
0.01
Occupation
HCW (formal and informal) 8/11 (72.7) 1.6 (1.1–2.5) 1.8 (0.91–3.6)
Ebola front-line worker 1/8 (12.5) 0.16 (0.02–1.5) 0.14 (0.02–1.3)
Driver 11/17 (64.7) 1.2 (0.67–2.0) 1.1 (0.55–2.3)
Religious leader/chief/teacher 5/7 (71.4) 1.6 (0.95–2.8) 1.8 (0.70–4.4)
Farmer/fisherman/unskilled 18/41 (43.9) 0.81 (0.49–1.4) 0.85 (0.48–1.5)
Office/business 26/39 (66.7) 1.3 (0.89–1.8) 1.4 (0.87–2.2)
Child/student 173/484 (35.7) 0.52 (0.40–0.69) 1.0 (0.63–1.6)
Trader/tailor/service
96/177 (54.2)
1
1


Water available
Sometimes 45/131 (34.4) 0.58 (0.2–-1.3) 0.59 (0.28–1.3)
Most days 118/265 (44.5) 1.0 (0.59–1.59) 0.96 (0.60–1.5)
Every day
182/408 (44.6)
1
1


Soap available
Sometimes 64/194 (33.0) 0.78 (0.42–1.4) 0.84 (0.47–1.5)
Most days 113/200 (56.5) 1.5 (0.90–5.5) 1.4 (0.84–2.3)
Every day
168/410 (41.0)
1
1


Latrine
Household’s own 107/286 (37.4) 0.7(0.43–1.2) 0.72 (0.43–1.2)
Shared/none
238/518 (45.9)
1
1


Crowding
High 126/238 (52.9) 2.1 (0.89–4.7) 2.4 (1.0–5.4)
Medium 189/483 (39.1) 1.4 (0.63–3.2) 1.6 (0.71–3.6)
Low
30/83 (36.1)
1
1


Spouse with Ebola first
Yes 45/77 (58.4) 1.6 (1.2–2.1) 1.0 (0.68–1.5)
No 302/732 (41.3) 1 1

*Subsequent case-patients were any household members who contracted Ebola virus disease after the first (primary) case-patient. Data were excluded for 4 deaths from uncertain cause, 27 persons with no individual-level data, and 97 primary cases. Data were missing for 2 persons with no recorded age, 6 persons with no recorded occupation, and 5 persons (in 1 household) with no recorded information about water, soap, latrine, and crowding. EVD, Ebola virus disease; HCW, healthcare worker; RR, risk ratio.
†Number of subsequent case-patients/total number of household members in study, excluding primary case-patients.
‡Adjusted for household clustering.
§Adjusted for age, sex, and household clustering.
¶Adjusted for clustering and all other factors included in the model.
#p values for multivariable model calculated from likelihood ratio test in logistic regression model.
**Only 7 persons reported no contact, so these 2 categories are combined.

Main Article

Page created: July 15, 2016
Page updated: July 15, 2016
Page reviewed: July 15, 2016
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