Assessment of exposure to influenza A viruses in pigs between weaning and market age

Table 4 Linear regression models for analysis of titers for influenza A based on the number of positive results

^‡The original titer divided by 10 and then log₂ transformed.
^\Pigs were positive twice. Reference category was that pigs were positive once.
^\\Pigs were positive 3 or 4 times. Reference category was that pigs were positive once.
^¥Pigs were positive once. Reference category was that pigs were never positive.
^¥¥Pigs were positive twice or 3 times. Reference category was that pigs were never positive.
^±P-value obtained by testing categorical variable using a partial likelihood test.

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