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Volume 13, Number 9—September 2007
Research

Effect of Interventions on Influenza A (H9N2) Isolation in Hong Kong’s Live Poultry Markets, 1999–2005

Eric H.Y. Lau*1, Y.H. Connie Leung*1, Li Juan Zhang*, Benjamin J. Cowling*, Sin Ping Mak†, Yi Guan*, Gabriel M. Leung*Comments to Author , and J. S. Malik Peiris*
Author affiliations: *The University of Hong Kong, Hong Kong Special Administrative Region, People’s Republic of China; †Government of the Hong Kong Special Administrative Region, People’s Republic of China;

Main Article

Table

Adjusted RR, associated 95% CI, and p values of Poisson generalized linear models for influenza (H9N2) virus isolation rates by poultry type*

Characteristic Chickens
 Minor poultry
Adjusted RR 95% CI p value Adjusted RR 95% CI p value
Time period
No rest-day 1.00 Reference 1.00 Reference
1 rest-day with quails 0.73 0.44–1.20 0.22 0.42 0.25–0.71 0.001
1 rest-day without quails 0.61 0.37–1.02 0.061 0.40 0.24–0.68 0.001
2 rest-days 0.56 0.29–1.09 0.09 0.37 0.16–0.82 0.01
Proportion of chickens imported, per 10% increase
 0.93
 0.74–1.17
 0.54
1.06
 0.77–1.45
 0.73
Total sales of
Chicken per 100,000 1.09 1.01–1.17 0.02 1.08 0.99–1.18 0.07
Minor poultry per 100,000 2.98 1.52–5.87 0.002 3.20 1.42–7.22 0.005
Chicken × minor poultry,
interaction term
 0.97
 0.95–0.99
 0.01
0.97
 0.94–0.99
 0.01
Ventilation system
Natural ventilation 1.00 Reference 1.00 Reference
MEAT system 1.02 0.77–1.34 0.91 1.12 0.83–1.51 0.48
Air-conditioned 0.57 0.30–1.08 0.09 0.93 0.50–1.72 0.82
Temperature, ºC 1.00 0.92–1.09 0.99 1.11 1.00–1.24 0.06
Relative humidity, %
 0.99
 0.97–1.00
 0.12
0.98
 0.97–1.00
 0.12
Seasonality term†
α (cosine component) 0.25 –0.21–0.71 0.29 –0.23 –0.75–0.29 0.38
β (sine component) 0.31 –0.19–0.81 0.23 0.72 0.13–1.30 0.02

*RR, relative risk; CI, confidence interval; MEAT, market economic air treatment.
†The seasonality coefficients α and β contribute to the estimated isolation rate in week t via the terms αcos(2πt/52) + βsin(2πt/52).

Main Article

1These authors contributed equally to this article.

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