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Table 4 Differences in farm characteristics between A(H1N1)pdm09v-positive and enzootic IAV-S-positive farmsa

From: Effect of herd size on subclinical infection of swine in Vietnam with influenza A viruses

Variable   A(H1N1)pdm09v-positive farms,
no. (%)
Enzootic IAV-S-positive farms,
no. (%)
P value*
Total number of pigs <50 4 (50.0 %) 0 (0.0 %)  
50 to 500 0 (0.0 %) 1 (6.7 %)  
500 to 1000 0 (0.0 %) 1 (6.7 %)  
>1000 4 (50.0 %) 13 (86.7 %) 0.01
Other animals on farm No 0 (0.0 %) 9 (60.0 %)  
Yes 8 (100.0 %) 5 (33.3 %)  
No answer 0 (0.0 %) 1(6.7 %) 0.01
Farm type Family-operated farm 4 (50.0 %) 2 (13.3 %)  
Corporate farm 4 (50.0 %) 13 (86.7 %) 0.13
Shower-in facility for humans No 3 (37.5 %) 2 (13.3 %)  
Yes 5 (62.5 %) 10 (66.7 %)  
No answer 0 (0.0 %) 3 (20.0 %) 0.24
Disinfection facility for vehicles No 3 (37.5 %) 4 (26.7 %)  
Yes 5 (62.5 %) 11 (73.3 %) 0.66
Type of operation Not farrow-to-finish 3 (37.5 %) 2 (13.3 %)  
Including farrow-to-finish 5 (62.5 %) 13 (86.7 %) 0.30
Type of pig house Open-sided or semi-open-sided house 8 (100.0 %) 13 (86.7 %)  
Windowless 0 (0.0 %) 2 (13.3 %) 0.53
Introduction of pigs from external source No 0 (0.0 %) 1 (6.7 %)  
Yes 7 (87.5 %) 11 (73.3 %)  
No information 1 (12.5 %) 3 (20.0 %) 1.00
Vaccination No 0 (0.0 %) 1 (6.7 %)  
Yes 5 (62.5 %) 14 (93.3 %)  
No answer 3 (37.5 %) 0 (0.0 %) 0.03
  1. *Fisher’s exact test was applied to compare proportions between A(H1N1)pdm09v positive- and enzootic IAV-S-positive- farms
  2. aOne farm from which both A(H1N1)pdm09 virus and an enzootic strain were isolated was included as being both A(H1N1)pdm09v-positive and enzootic-positive