Volume 22, Number 8—August 2016
Research
Exposure-Specific and Age-Specific Attack Rates for Ebola Virus Disease in Ebola-Affected Households, Sierra Leone
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.