Table 3.

Unadjusted odds ratios for risk factors associated with influenza A molecular positivity among 396 environmental water samples collected from six Chinese pig farms (three farms from Shandong and three farms from Jiangsu Province) between March 2015 and February 2016

	Environmental water influenza A positive
Risk factor	Total N	No. (%)	Unadjusted OR (95% CI)
Temperature outside of sampled barn (°C)
−5.0–4.9	72	2 (2.8)	0.16 (0.03–0.78)
5.0–13.9	48	2 (4.2)	0.25 (0.05–1.20)
14.0–23.9	42	5 (11.9)	1.27 (0.41–3.89)
24.0–29.9	120	3 (2.5)	0.15 (0.04–0.56)
≥30.0	60	9 (15.0)	Ref.
Fecal slurry sample influenza A virus positivity
Positive	19	5 (26.3)	7.12 (2.31–21.95)
Negative	377	18 (4.8)	Ref.
Environmental surface swab sample influenza A virus positivity
Positive	46	7 (15.2)	3.75 (1.45–9.67)
Negative	350	16 (4.6)	Ref.
Bioaerosol sampling influenza A virus positivity
Positive	20	3 (15.0)	3.14 (0.85–11.61)
Negative	376	20 (5.3)	Ref.

CI confidence interval

ORs significant with a p-value < 0.05 are indicated in bold text