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A total of 215 nontypeable rotavirus samples collected from children <5 years of age by members of the African Rotavirus Network were characterized using reverse-transcription polymerase chain reaction analysis and sequencing. The most predominant strain identified was P[8]G1 (46.9%). Genotypes P[8]G10, P[8]G8, P[6]G8, and P[7]G5 were also detected at frequencies varying from 0.5% to 2.3%. This study suggests that reassortment of unusual G types into a background of globally common genotype P[8] strains may be a major mechanism of generating rotavirus diversity. Nucleotide substitutions at the P[8], P[6], and G1 primer binding sites accounted for the failure to type these strains initially. Hence, these findings highlight the need for regular evaluation of rotavirus genotyping methods.

Global rotavirus surveillance has led to the detection of many unusual human rotavirus (HRV) genotypes. During 1996-2004 surveillance within the African Rotavirus Network (ARN), six P[8],G8 and two P[6],G8 human rotavirus strains were identified. Gene fragments (RT-PCR amplicons) of all 11-gene segments of these G8 strains were sequenced in order to elucidate their genetic and evolutionary relationships. Phylogenetic and sequence analyses of each gene segment revealed high similarities (88-100% nt and 91-100% aa) for all segments except for gene 4 encoding VP4 proteins P[8] and P[6]. For most strains, almost all of the genes of the ARN strains other than neutralizing antigens are related to typical human strains of Wa genogroup. The VP7, NSP2, and NSP5 genes were closely related to cognate genes of animal strains (83-99% and 97-99% aa identity). This study suggests that the ARN G8 strains might have arisen through VP7 or VP4 gene reassortment events since most of the other gene segments resemble those of common human rotaviruses. However, VP7, NSP2 (likely), and NSP5 (likely) genes are derived potentially from animals consistent with a zoonotic introduction. Although these findings help elucidate rotavirus evolution, sequence studies of cognate animal rotavirus genes are needed to conclusively determine the specific origin of those genes relative to both human and animal rotavirus strains., (Copyright 2009 Wiley-Liss, Inc.)