Emergence of G9 P[6] human rotaviruses in Argentina: Phylogenetic relationships among G9 strains

Because rotavirus diarrhea can be reduced through vaccination and because c urrent vaccine candidates provide protection against only the most common G antigenic types (G1 to G4), detection of uncommon G types is one of the ma in goals of rotavirus surveillance. After a 2-year nationwide rotavirus sur veillance study in Argentina concluded, surveillance was continued and an i ncrease of G9 prevalence in several Argentine cities was detected. During t his period G9 strains predominated in the south, and a gradient of decreasi ng G9 prevalence was observed from south to north (41 to 0%). Sequence anal ysis of gene 9, encoding the G antigen, showed that Argentine strains clust er with most G9 isolates from other countries, showing less than 2% nucleot ide divergence among them, but are distinctive from them in that they prese nt some unique amino acid changes. Our results agree with reports of increa sed G9 prevalence in other parts of the world, suggesting the need to incor porate G9 into candidate rotavirus vaccines.