Volume 13, Number 9—September 2007
Research
Effect of Interventions on Influenza A (H9N2) Isolation in Hong Kong’s Live Poultry Markets, 1999–2005
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).