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Volume 12, Number 12—December 2006

Research

Risk Factors for Human Infection with Avian Influenza A H5N1, Vietnam, 2004

Pham Ngoc Dinh*, Hoang Thuy Long*, Nguyen Thi Kim Tien†, Nguyen Tran Hien*, Le Thi Quynh Mai*, Le Hong Phong*Comments to Author , Le Van Tuan†, Hoang Van Tan*, Nguyen Binh Nguyen*, Phan Van Tu†, Nguyen Thi Minh Phuong†, and the World Health Organization/Global Outbreak Alert and Response Network Avian Influenza Investigation Team in Vietnam
Author affiliations: *National Institute of Hygiene and Epidemiology, Hanoi, Vietnam; †Pasteur Institute, Ho Chi Minh City, Vietnam

Main Article

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.

*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.

*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.

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