Genetic Diversity and Amino Acid Substitutions among Norovirus Genogroup II Strains in Environmental and Stool Samples

Abstract

Capsid gene sequences of norovirus GII were acquired from patients of gastroenteritis, primary-treated wastewater, activated sludge, secondary-treated wastewater, river water, seawater and oyster in geographically close areas between 2001 and 2006. Most of the norovirus GII genes acquired from gastroenteritis patients were mainly categorized into GII.3 and GII.4. On the other hand, diverse genotypes of norovirus GII including GII.2, 3, 4, 5, 10, 11, 14and 15 were obtained from environmental samples. Amino acid sequences of norovirus GII.4 obtained in this study were compared with that of norovirus GII.4 Bristol. As a result, amino acid substitutions were observed in the 8th (Ala), 9th (Asn), 15th (Ala) and 54th (Asn) residues. The analysis of amino acid substitutions and investigation of the appearance of norovirus mutants could be useful to understand the dynamics of norovirus in human society.