Models fit and nested model comparisons made using the likelihood ratio test (chi-squared test, df = degrees of freedom).

Models are specified by their logistic and linear components, with “A” indicating a term for animal was in the model component, “V” indicating a term for virus was in the model component, and “I” the interaction between animal and virus was in the model component. For convenience, model labels are given in the first column (Model), and the nested/reduced model being compared to that is given as the Comparator Model, referenced by the Model label of column one. P-values <0.05 are in boldface.