Likelihood ratio tests (LRTs) for positive selection.

LRTs revealed none of the amino acid sites of E2 in each patient was under positive selection at p2Δl: Differences between the likelihood scores of null (M7) and alternative model (M8).The p-values were calculated with degrees of freedom = 2.Null model (M7) that assumes neutral evolution was compared with the model (M8) that assumes positive selection.