Table 1. Epidemiologic data for influenza A virus among swine in coordinated swine production systems, United States, September 2012–September 2013*.
| Variable | No. samples | No. (%) positive samples | p value |
|---|---|---|---|
| State* | |||
| Georgia | 2,520 | 73 (2.9) | |
| Illinois | 4,490 | 408 (9.1) | <0.001 |
| Nebraska | 3,894 | 126 (3.2) | |
| Oklahoma |
4,050 |
134 (3.3) |
|
| Age group | |||
| Gilt | 8,028 | 375 (4.7) | 0.85 |
| Piglet |
6,926 |
366 (5.3) |
|
| Farm type | |||
| MF, gilts† | 1,526 | 67 (4.4) | |
| MF, piglets | 1,559 | 72 (4.6) | |
| GDU | 1,455 | 115 (7.9) | <0.001 |
| BTW |
10,414 |
487 (4.7) |
|
| System | |||
| 1 | 3,673 | 142 (3.9) | |
| 2 | 3,337 | 339 (10.2) | <0.001 |
| 3 | 4,050 | 134 (3.3) | |
| 4 | 3,894 | 126 (3.2) | |
*Piglets were sampled before weaning; gilts were sampled at entry to MFs and before moving from GDUs to BTWs. MF, multiplier farm; GDU, gilt development unit; BTW, breed-to-wean.