s2m in caliciviruses. (A) Phylogenetic analysis of caliciviruses using partial RNA-dependent RNA polymerase sequences (265 amino acids) and maximum likelihood (RAxML). Bootstrap values > 80% have been indicated and s2m-containing sequences have been highlighted (boldface/underscore). (B) Secondary structure of norovirus s2m sequences folded using mfold . Box and arrow indicate nucleotide positions that vary within the noroviruses. * - The two copies of s2m found in Norovirus dog (GVI.1/HKU_Ca026F/2007/HKG) and Norovirus dog (GVI.1/HKU_Ca035F/2007/HKG).