Table 1. Matched-pair analysis of potential risk factors for human infection with avian influenza A H5N1, Vietnam, 2004.
| Exposure and characteristics | Case-patients (n = 28), n (%) | Control-respondents (n = 106), n (%) | Matched OR* (95% CI) | p value |
|---|---|---|---|---|
| High school, college, or university education (persons >14 y of age) | 8 (53)† | 17 (29)‡ | 16.0 (1.2–594.1) | 0.03 |
| Family size >5 persons | 8 (29) | 32 (30) | 1.2 (0.4–4.0) | 0.88 |
| Ever smoked | 3 (11) | 10 (9) | 2.0 (0.1–30.5) | 0.91 |
| Chronic medical conditions | 3 (11) | 9 (8) | 1.3 (0.2–7.7) | 0.93 |
| Poultry-related exposures§ | ||||
| Prepared and cooked healthy poultry | 9 (32) | 24 (23) | 2.2 (0.6–10.4) | 0.249 |
| Prepared and cooked sick or dead poultry | 9 (32) | 6 (6) | 31.0 (3.4–1150) | <0.001 |
| Helped prepare or cook sick or dead poultry | 7 (25) | 12 (11) | 2.6 (0.8–8.7) | 0.102 |
| Bought live poultry for household consumption | 3 (11) | 9 (8) | 1.2 (0.2–7.0) | 0.895 |
| Bought freshly killed poultry for household consumption | 0 (0) | 11 (10) | Incalculable | - |
| Live poultry in household | 18 (64) | 52 (49) | 3.0 (0.9–10.0) | 0.103 |
| Sick or dead poultry in household | 15 (54) | 20 (19) | 7.4 (2.7–59.0) | <0.001 |
| Live poultry in neighborhood | 19 (79)¶ | 75 (74)# | 1.07 (0.2–6.6) | 0.810 |
| Sick or dead poultry in neighborhood | 12 (43) | 29 (27) | 3.9 (1.0–55.7) | 0.05 |
| Farm or family with >150 poultry within 100 m | 4 (14) | 16 (15) | 1.0 (0.2–4.2) | 0.742 |
| Household members work with commercial poultry | 1 (4) | 2 (2) | 2.0 (0.0–38.4) | 0.88 |
| Other animal-related exposures | ||||
| Pigs in household | 9 (32) | 28 (26) | 1.4 (0.3–6.4) | 0.838 |
| Pig in neighborhood | 15 (54) | 48 (45) | 2.0 (0.5–7.2) | 0.505 |
| Dogs in household | 18 (64) | 58 (55) | 1.7 (0.6–4.7) | 0.430 |
| Cats in household | 9 (32) | 23 (22) | 2.0 (0.6–5.9) | 0.374 |
| Buffalo in household | 1 (4) | 1 (1) | 4.0 (0.1–314) | 0.86 |
| Cows in household | 5 (18) | 14 (13) | 2.4 (0.3–17.4) | 0.581 |
| Human-related exposures§ | ||||
| Exposed to patients with acute respiratory infection (temperature ≥38°C) | 6 (21) | 11 (10) | 2.4 (0.7–13.5) | 0.145 |
| Exposed to hospitalized patients with acute respiratory infection | 5 (18) | 9 (8) | 2.4 (0.6–12.9) | 0.210 |
| Hygiene- and environment-related exposures | ||||
| Handwashing before eating (usually or sometimes) | 23 (82) | 90 (85) | 1.3 (0.3–5.6) | 0.911 |
| Handwashing >3 times/d | 25 (89) | 87 (82) | 0.53 (0.1–2.4) | 0.568 |
| Wading in ponds, rice fields, ditches | 4 (14) | 7 (7) | 2.4 (0.4–19.2) | 0.469 |
| No indoor water source in household | 22 (79) | 64 (60) | 5.0 (1.3–77.0) | 0.024 |
| Poor hygiene conditions** | 12 (43) | 47 (44) | 1.0 (0.3–3.4) | 0.829 |
*Matched analysis using McNemar (Mantel-Haenszel) test statistics; 95% confidence limits are exact intervals for maximum likelihood estimate; OR, odds ratio; CI, confidence interval. †n = 15. ‡n = 58. §7 d before illness onset in case-patient. ¶n = 24. #n = 102. **A composite measure of 7 indicators: dust level in person’s home, type of flooring, frequency of house cleaning, habit of washing hands before eating, habit of washing fruit before eating, estimated frequency of handwashing/d, and interviewer’s assessment of household cleanliness.