Application of next-generation sequencing to investigation of norovirus diversity in shellfish collected from two coastal sites in Japan from 2013 to 2014.

A better understanding of the role played by shellfish regarding the manner of pathogen contamination, persistence, and selection may help considering epidemiology of noroviruses. Thus, norovirus genotype profiles in shellfish (Crassostrea gigas and Mitilus galloprovincialis) were investigated by using Next-generation sequencing (NGS) technology. In genogroup I (GI), 7 genotypes (abbreviated as GI.2 to GI.7, and GI.9) were detected from C. gigas, whereas 9 genotypes (GI.1 to GI.9) were detected from M. galloprovincialis. The genotype with the highest proportion found in both C. gigas and M. galloprovincialis was GI.4, and the second highest was GI.3. In genogroup II (GII), 17 genotypes (GII.1 to GII.9, GII.11 to GII.17, GII.21 and GI.22) were detected from C. gigas, whereas 16 genotypes (GII.1 to GII.8, GII.11 to GII.17, GII.21 and GI.22) were detected from M. galloprovincialis. The genotype with the highest proportion in both C. gigas and M. galloprovincialis was GII.4, the next highest differed between C. gigas and M. galloprovincialis. To our knowledge, this study may be the first trial to utilize the latest technology in this field, and reveal the diversity of norovirus genotypes present in shellfish.