Table 3.
Univariate matched-pair analyses of potential H5N1 risk factors, overall and stratified by urban and rural groups, China
| Overall Participants | Rural Participants | Urban Participants | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Potential risk factors a | Cases n=28, (%) |
Controls n=134, (%) |
OR (95% CI) | P b | Cases n=18, (%) |
Controls n=85, (%) |
OR (95% CI) | P b | Cases n=10, (%) |
Controls n=49, (%) |
OR (95% CI) | P b |
| Underlying medicalcondition | 5 (18) | 6 (4) | 5.2 (1.3–19.9) | 0.018 | 3 (17) | 4 (5) | 5.6 (0.9–36.3) | 0.073 | 2 (20) | 2 (4) | 4.7 (0.7–33.6) | 0.121 |
| Travel history c | 4 (14) | 20 (15) | 1.0 (0.3–3.6) | 0.964 | 1 (6) | 13 (15) | 0.2 (0.0–2.4) | 0.208 | 3 (30) | 7 (14) | 2.8 (0.5–15.2) | 0.222 |
| Occupational poultry exposure d | 4 (14) | 5 (4) | 13.1 (1.4–125.4) | 0.026 | 3 (17) | 5 (6) | 8.3 (0.8–90.1) | 0.081 | 1 (10) | 0 (0) | NA e | NA e |
| Exposures to backyard poultry | ||||||||||||
| Raise backyard poultry | 15 (54) | 48 (36) | 4.5 (1.1–17.5) | 0.031 | 15 (83) | 48 (56) | 4.5 (1.1–17.5) | 0.031 | 0 (0) | 0 (0) | - | - |
| Location of backyard poultry cage | ||||||||||||
| No backyard poultry | 13 (46) | 86 (64) | ref f | ref f | 3 (17) | 37 (44) | ref f | ref f | - | - | - | - |
| Present outside home | 9 (32) | 37 (28) | 3.7 (0.9–15.3) | 0.071 | 9 (50) | 37 (44) | 3.7 (0.9–15.3) | 0.071 | - | - | - | - |
| Present inside house | 6 (22) | 11 (8) | 9.7 (1.8–53.3) | 0.009 | 6 (33) | 11 (12) | 9.7 (1.8–53.3) | 0.009 | - | - | - | - |
| Raise domestic waterfowl g or chickens | ||||||||||||
| No backyard poultry | 13 (46) | 86 (64) | ref f | ref f | 3 (17) | 37 (44) | ref f | ref f | - | - | - | - |
| Only raise chickens | 7 (25) | 34 (25) | 2.6 (0.6–12.1) | 0.226 | 7 (39) | 34 (40) | 2.6 (0.6–12.1) | 0.226 | - | - | - | - |
| Raise waterfowl | 8 (29) | 14 (11) | 6.4 (1.6–26.3) | 0.010 | 8 (44) | 14 (16) | 6.4 (1.6–26.3) | 0.010 | - | - | - | - |
| Backyard poultry H5 vaccination | ||||||||||||
| No backyard poultry | 13 (46) | 86/124 (70) | ref f | ref f | 3 (17) | 37/75 (50) | ref f | ref f | - | - | - | - |
| Backyard poultry | ||||||||||||
| H5 vaccination coverage ≥ 80% | 6 (22) | 19/124 (15) | 4.0 (0.9–17.9) | 0.070 | 6 (33) | 19/75 (25) | 4.0 (0.9–17.9) | 0.070 | - | - | - | - |
| Backyard poultry | ||||||||||||
| H5 vaccination coverage < 80% | 9 (32) | 19/124 (15) | 7.1 (1.6–31.6) | 0.010 | 9 (50) | 19/75 (25) | 7.1 (1.6–31.6) | 0.010 | - | - | - | - |
| Domestic waterfowl H5 vaccination | ||||||||||||
| No domestic waterfowl | 20 (71) | 120/132 (91) | ref f | ref f | 10 (55) | 71/83 (86) | ref f | ref f | - | - | - | - |
| Domestic waterfowl | ||||||||||||
| H5 vaccination coverage ≥ 80% | 3 (11) | 7/132 (5) | 2.4 (0.5–11.2) | 0.257 | 3 (17) | 7/83 (8) | 2.4 (0.5–11.2) | 0.257 | - | - | - | - |
| Domestic waterfowl | ||||||||||||
| H5 vaccination coverage < 80% | 5 (18) | 5/132 (4) | 8.4 (1.6–45.1) | 0.013 | 5 (28) | 5/83 (6) | 8.4 (1.6–45.1) | 0.013 | - | - | - | - |
| Exposures to well-appearing poultry | ||||||||||||
| Direct contact | 11/27 (41) | 31/133 (23) | 3.3 (1.0–10.4) | 0.043 | 9/17 (53) | 27 (32) | 2.9 (0.8–10.4) | 0.099 | 2 (20) | 4/48 (8) | 5.3 (0.4–70.8) | 0.206 |
| Only indirect contact (<1 meter) | 8/26 (31) | 43/133 (32) | 0.8 (0.3–2.4) | 0.724 | 7/17 (41) | 40/84 (48) | 0.7 (0.2–2.3) | 0.594 | 1/9 (11) | 3 (6) | 1.6 (0.1–19.4) | 0.713 |
| Consumed well-appearing poultry | 22 (79) | 99 (74) | 1.3 (0.4–4.2) | 0.610 | 12 (67) | 59 (69) | 0.8 (0.2–2.8) | 0.689 | 10 (100) | 40 (82) | NA e | NA e |
| Exposures to sick/dead poultry | ||||||||||||
| Direct contact with sick/dead poultry | 9 (32) | 4/133 (3) | 34.7 (4.3–276.9) | 0.001 | 8 (44) | 4/84 (5) | 29.8 (3.7–241.5) | 0.001 | 1 (10) | 0 (0) | NA e | NA e |
| Only indirect contact with sick/dead poultry (<1 meter) | 6 (21) | 4/132 (3) | 11.3 (2.2–58.5) | 0.004 | 6 (33) | 4/83 (5) | 11.3 (2.2–58.5) | 0.004 | - | - | - | - |
| Consumed sick/dead poultry | 11 (39) | 1 (1) | NA e | NA e | 10 (56) | 1 (1) | NA e | NA e | 1 (10) | 0 (0) | NA e | NA e |
| Wet poultry market exposures | ||||||||||||
| Visited wet poultry market | 17 (61) | 51/133 (38) | 3.1 (1.2–7.9) | 0.019 | 7 (39) | 29/84 (35) | 1.2 (0.4–3.8) | 0.725 | 10 (100) | 22 (45) | NA e | NA e |
| Visited wet poultry market and witnessed poultry slaughtering at market | 15 (54) | 35/129 (27) | 5.0 (1.7–14.9) | 0.004 | 6 (33) | 17/83 (20) | 2.2 (0.6–7.7) | 0.224 | 9 (90) | 18/46 (39) | NA e | NA e |
| Frequency of visiting wet poultry market within last 2 weeks | ||||||||||||
| Never (%) | 11/27 (41) | 82/131 (63) | ref f | ref f | 11/17 (65) | 55/82 (67) | ref f | ref f | 0 (0) | 27 (55) | ref f | ref f |
| 1–5 times (%) | 8/27 (30) | 27/131 (20) | 2.8 (0.9–8.1) | 0.062 | 4/17 (23) | 17/82 (21) | NA e | NA e | 4 (40) | 10 (21) | NA e | NA e |
| 6–10 times (%) | 3/27 (11) | 8/131 (6) | 7.6 (1.1–53.7) | 0.043 | 2/17 (12) | 2/82 (2) | NA e | NA e | 1 (10) | 6 (12) | NA e | NA e |
| >10 times (%) | 5/27 (18) | 14/131 (11) | 5.8 (1.2–28.6) | 0.031 | 0/17 (0) | 8/82 (10) | NA e | NA e | 5 (50) | 6 (12) | NA e | NA e |
| Contact with live poultry in the market | ||||||||||||
| No contact | 22/27 (82) | 120/133 (90) | ref f | ref f | 14/17 (82) | 78/84 (92) | ref f | ref f | 8 (80) | 42 (86) | ref f | ref f |
| Only indirect contact with live poultry (<1 meter) | 3/27 (11) | 9/133 (7) | 1.9 (0.4–8.1) | 0.411 | 2/17 (12) | 3/84 (4) | 3.0 (0.5–19.2) | 0.247 | 1 (10) | 6 (12) | NA e | NA e |
| Direct contact with live poultry | 2/27 (7) | 4/133 (3) | 4.6 (0.4–51.9) | 0.222 | 1/17 (6) | 3/84 (4) | 2.4 (0.1–41.3) | 0.534 | 1 (10) | 1 (2) | NA e | NA e |
| Exposure to animals h | ||||||||||||
| Raise backyard animals | 15 (54) | 61 (46) | 1.4 (0.6–3.7) | 0.459 | 14 (78) | 50 (59) | 2.5 (0.7–8.9) | 0.145 | 1 (10) | 11 (22) | 0.4 (0.0–3.2) | 0.367 |
| Direct contact with backyard animals | 8 (29) | 38 (28) | 1.0 (0.4–2.6) | 0.987 | 7 (39) | 27 (32) | 1.4 (0.5–4.0) | 0.548 | 1 (10) | 11 (22) | 0.4 (0.0–3.4) | 0.368 |
| Lack of indoor water supply | 14 (50) | 68 (51) | 0.7 (0.1–4.3) | 0.726 | 14 (78) | 68 (80) | 0.7 (0.1–4.3) | 0.726 | 0 (0) | 0 (0) | - | - |
| Exposed to persons with fever and respiratory symptoms | 1 (4) I | 0 (0) | NA e | NA e | 1 (6) i | 0 (0) | NA e | NA e | 0 (0) | 0 (0) | - | - |
| Exposed to confirmed human H5N1 case-patients | 1 (4) j | 0 (0) | NA e | NA e | 0 (0) | 0 (0) | - | - | 1 (10) j | 0 (0) | NA e | NA e |
a
The denominators for calculation in fewer than the full groups were indicated.
b
Comparison of frequencies between cases and controls were analyzed by exact conditional logistic regression. When matched OR and p value were calculated, data for matched controls were excluded for cases with missing exposure data, and controls with missing data were dropped from analyses, but not the matched case or other controls with available data.
c
Travel outside of home-township (for rural cases) or outside of home city (for urban cases) for >24 hours in the 2 weeks prior to the case’s illness onset.
d
Defined as workplace exposure to live poultry (e.g., poultry farm/factory, wet poultry market), not including backyard poultry exposure
e
Not available, due to small sample size or data distribution could not be analyzed by conditional logistic regression
f
ref: reference.
g
Includes ducks and geese.
h
Includes cats, pigs, dogs, cows and goats.
i
A family cluster was reported in reference 15.
j
A family cluster consisting of a confirmed son and his father was reported in reference 8.