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Volume 13, Number 3—March 2007
Research

Risk for Infection with Highly Pathogenic Influenza A Virus (H5N1) in Chickens, Hong Kong, 2002

Nina Y. Kung*†1Comments to Author , Roger S. Morris*, Nigel R. Perkins*, Les D. Sims‡, Trevor M. Ellis‡, Lucy Bissett‡, Mary Chow‡, Ken F. Shortridge‡, Yi Guan‡, and Malik J.S. Peiris‡
Author affiliations: *Massey University, Palmerston North, New Zealand; †University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, People’s Republic of China; ‡Department of Agriculture, Fisheries and Conservation, Kowloon, Hong Kong Special Administrative Region, People’s Republic of China;

Main Article

Table 3

Results of univariate analysis of risk factors for avian influenza type A virus (H5N1) infection among chicken farms, Hong Kong, 2002*

VariableCategoryCaseControlOR95% CIp value
Farm profile
Pig farm within 500 m
13
29
2.54
0.63–10.21
0.226
No pig farm within 500 m
3
17
1
Stock
No. chickens on the farm
NA
NA
NA
NA
<0.001
Stock density (chicken no./farm area )
NA
NA
NA
NA
0.007
Age group with highest death rate
Most deaths in birds ≥30 d old
5
3
7.40
1.49–36.82
0.017
Most deaths in birds <30 d old
9
40
1
Survival rate
≥90% at 1–30 d
15
28
1.54
1.23–1.91
0.003
<90% at 1–30 d
0
18
1
≥90% at 30–60 d
11
42
0.26
0.06–1.22
0.093
<90% at 30–60 d
4
4
1
≥90% at >60 d
13
44
0.20
0.03–1.31
0.103
<90% at >60 d
3
2
1
Medication given? (Jan–Feb 2002)
Yes
12
18
4.67
1.30–16.74
0.020
No
4
28
1
Were wild birds seen eating in feed troughs?
Yes
10
41
0.20
0.04–0.86
0.036
No
5
4
1
Could wild birds gain entry into the shed?
Yes
13
44
0.10
0.01–1.03
0.052
No
3
1
1
Does the farm sell chickens directly to a retail market?
Yes
7
3
11.15
2.41–51.56
0.002
No
9
43
1
Installed automatic manure scrapers in shed
Yes
11
15
4.55
1.34–15.46
0.018
No
5
31
1
Farm owner lives on farm
Yes
7
43
0.05
0.01–0.25
<0.001
No
9
3
1
Farm owner owns or partly owns another chicken farm
Yes
3
2
5.08
0.77–33.71
0.103
No
13
44
1
Farmer has relatives working in the poultry industry
Yes
4
5
2.73
0.63–11.81
0.219
No
12
41
1
Visitors from another chicken farm?
Yes
2
0
0.23
0.15–0.37
0.015
No
14
46
1
Visitors from retail markets?
Yes
5
2
10.00
1.71–58.59
0.010
No
11
44
1
Visitors went inside sheds?
Yes
7
8
3.94
1.03–15.13
0.040
No
6
27
1
District
Within main affected area
15
5
123.00
13.27–1140.46
0.000
Outside main affected area1411

*Variables for which p value is >0.25 have been excluded. OR, odds ratio; CI, confidence interval; NA, not applicable.

Main Article

1Current affiliation: AgriQuality Ltd, Lower Hutt, New Zealand

Page created: June 29, 2010
Page updated: June 29, 2010
Page reviewed: June 29, 2010
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
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