Diversity of group A rotavirus strains circulating in Paraguay from 2002 to 2005 : Detection of an atypical G1 in South America

Abstract Background Group A rotaviruses are the main cause of severe gastroenteritis in children worldwide. Objectives To survey human rotavirus strains circulating in Paraguay. Study design One hundred ninety-six rotavirus-positive fecal samples collected from children up to 5 years old, from 2002 to 2005, were characterized. Results The most common G genotype detected was G9 (36.2%), followed by G1 (34.2%), G2 (11.7%) and G4 (8.7%). Changes in the G genotype frequency were observed from year to year. The G4 genotype was predominant in 2002; G1 in 2003; and G9 from 2004 to 2005. Sequence and phylogenetic analysis of the VP7 gene from Paraguayan G1 strains suggested that the high frequency of G1 in 2003 could be due to the introduction of an atypical sub-lineage. In addition, there were amino acid changes in the variable/antigenic regions of the VP7 gene from G4 and G9 strains detected in different years. Conclusions This study further indicates that antigenic pressure can drive the evolution of rotaviruses, and also suggests that a vaccine that protects against the most prevalent strains and its variants, will be necessary to elicit a protective immune response against the range of rotavirus types currently circulating in Paraguay.