Table 3. Model 2 — Risk factors associated with Avian Influenza type H9N2 infection on commercial poultry farms in Pakistan based on a backward manual stepwise selection process on all variables available in Table 1 except distance to the nearest case farm.

Potential risk factors	Levels	Regression coefficient	Standard error	Odds ratios	95% CI for OR	p-value
Distance from the main road	>0.5km			1
	≤0.5km	1.5244	0.7328	4.59 a	1.09–19.3	0.038
Cover on the water tank	No water tank			1
	No cover	0.8490	0.9830	2.34	0.34–16.1	0.388
	Yes cover	-1.1604	0.7767	0.3130 b*¶	0.068–1.44	0.135
History of Infectious Bursal Disease in the flock	No			1
	Yes	1.0979	0.3741	3.00 c	1.44–6.24	0.003
Selling of birds/eggs directly to the live bird retail stalls	No			1
	Yes	2.3598	0.5847	10.6 d	3.37–33.3	<0.001

R² = 0.235 (out of possible 0.5)

^aThe odds of having the distance from the main road <0.5km was 4.59 (CI 95%: 1.09–19.3) times higher than the odds of exposure in the control farms.

^b*¶Non significant protective factor, i.e odds of having cover on the water storage tank on case farm was 0.313 (CI 95%: 0.068–1.44) times less than the odds of having cover on the water storage tank on control farms.

^cThe odds of having history of infection with IBD for case was 3.00 (95% CI: 1.44–6.24) times greater than the odds of exposure in the control farm.

^dThe odds of selling the birds/and or eggs directly to live bird retail shops was 10.6 (CI 95%: 3.37–33.3) times more than the odds of exposure in the control farms.