Detection of substantial porcine group B rotavirus genetic diversity in the United States, resulting in a modified classification proposal for G genotypes

► Porcine RBV strains found in 46.8% of samples tested in the United States in 2009. ► Majority of RVB-positive samples (86.4%) contained mixed RV infections. ► Unexpected higher prevalence of RVC (50.0%) than RVA (27.1%) in <21 days age group. ► High detection rate (24.3%) of RVA/RVB/RVC co-infections. ► Updated RVB VP7 classification, using 80% nucleotide cutoff, yields 20 G genotypes.