Table 5.
Unadjusted odds ratios for risk factors associated with influenza A molecular positivity among 396 fecal/slurry samples collected from six Chinese pig farms (three farms from Shandong and three farms from Jiangsu Province) between March 2015 and February 2016
| Fecal/slurry influenza A positive | |||
|---|---|---|---|
| Risk factor | Total N | No. (%) | Unadjusted OR (95% CI) |
| Total number of pigs on site | |||
| ≥3000 | 36 | 6 (16.7) | 13.0 (1.50–112.81) |
| 2000–2999 | 84 | 2 (2.4) | 1.59 (0.14–17.87) |
| 1000-1999 | 156 | 9 (5.8) | 3.98 (0.49–32.06) |
| <1000 | 66 | 1 (1.5) | Ref. |
| Total number of non-swine animals onsitea | |||
| ≥30 | 60 | 10 (16.7) | 10.0 (2.11–47.38) |
| 20–29 | 102 | 3 (2.9) | 1.52 (0.25–9.26) |
| 10–19 | 78 | 3 (3.9) | 2.0 (0.33–12.27) |
| <10 | 102 | 2 (2.0) | Ref. |
| Temperature outside of sampled barn (°C) | |||
| −5.0–4.9 | 72 | 1 (1.4) | 0.41 (0.04–4.62) |
| 5.0–13.9 | 48 | 3 (6.3) | 1.93 (0.31–12.07) |
| 14.0–23.9 | 42 | 7 (16.7) | 5.8 (1.14–29.50) |
| 24.0–29.9 | 120 | 5 (4.2) | 1.26 (0.24–6.70) |
| ≥30.0 | 60 | 2 (3.3) | Ref. |
| Season sample was collectedb | |||
| Winter | 72 | 2 (2.8) | 3.06 (0.27–34.36) |
| Fall | 108 | 10 (9.3) | 10.92 (1.37–86.86) |
| Summer | 108 | 6 (5.6) | 6.29 (0.74–53.2) |
| Spring | 108 | 1 (0.9) | Ref. |
| Age of pigs in weeks near where samples were collected (quintiles) | |||
| 105.0–208.0 (Q5) | 62 | 8 (12.9) | 5.23 (1.33–20.53) |
| 53.0–104.0 (Q4) | 91 | 1 (1.1) | 0.39 (0.04–3.84) |
| 21.0–52.0 (Q3) | 51 | 5 (9.8) | 3.84 (0.88–16.75) |
| 13.0–20.0 (Q2) | 83 | 2 (2.4) | 0.87 (0.14–5.34) |
| 1.0–12.0 (Q1) | 109 | 3 (2.8) | Ref. |
| Environmental water sample influenza A virus positivity | |||
| Positive | 23 | 5 (21.7) | 3.75 (1.45–9.67) |
| Negative | 373 | 14 (3.8) | Ref. |
| Environmental surface swab sample influenza A virus positivity | |||
| Positive | 46 | 7 (15.2) | 5.06 (1.88–13.60) |
| Negative | 350 | 12 (3.4) | Ref. |
| Bioaerosol sampling influenza A virus positivity | |||
| Positive | 20 | 3 (15.0) | 2.72 (0.94–7.89) |
| Negative | 376 | 16 (4.3) | Ref. |
CI confidence interval
1ORs significant with a p-value < 0.05 are indicated in bold text
aNon-swine animals include poultry and dogs
bSeasonality: spring (March 23, 2015 through June 20, 2015), summer (June 21, 2015 through Sept. 22, 2015), fall (Sept. 23, 2015 through Dec. 20, 2015), winter (Dec. 21, 2015 through Feb. 25, 2016)