Table 2. Relative risks for introduction of low pathogenicity avian influenza virus infection in different types of poultry farms, the Netherlands, 2007–2013.

Type of poultry farm	Relative risk (95% CI)	p value
Indoor-layer	1.0 (reference)
Outdoor-layer	6.3 (4.7–8.6)	<0.00001
Layer-breeder	0.5 (0.3–0.8)	0.008
Broiler	0.2 (0.1–0.8)	0.02
Broiler-breeder	0.4 (0.2–0.8)	0.004
Meat-turkey	12.0 (7.8–18.8)	<0.00001
Turkey-breeder	11.3 (2.8–46.2)	0.0008
Meat-duck	39.5 (22.6–69.1)	<0.00001
Duck-breeder	25.5 (14.2–45.9)	<0.00001
Natural logarithm*	0.8 (0.7–0.9)	0.00005

*Of distance to medium-sized waterways in meters, i.e., 3–6 m wide.