Aims: Norovirus (NoV) is a common foodborne virus in bivalve molluscs. This study aimed to identify genotypes of NoV genogroups I and II (GI and GII) in Asiatic hard clam (Meretrix meretrix) marketed in Hanoi, Viet Nam, in 2016.

Methods: A total of 39 Asiatic hard clam samples positive for NoV GI and/or NoV GII was genotyped using nested RT-PCR targeting fragment spanning the ORF1/ORF2 overlap region. PCR products were sequenced using Sanger sequencing and phylogenetic analysis was carried out using MEGA 11 software.

Results: NoV genotyping has been successfully performed for 23 samples. For NoV GI, four genotypes were detected: GI.2 (13.3%), GI.5 (46.7%), GI.6 (33.3%) and GI.8 (6.7%). We found five distinct genotypes of NoV GII, including GII.3 (61.1%), GII.4 (11.1%), GII.6 (11.1%), GII.13 (11.1%) and GII.17 (5.6%). Phylogenetic analysis revealed these NoV genotypes displayed high similarity with clinical strains circulating worldwide, especially strains from Asian countries.

Conclusions: The contamination of NoV GI and NoV GII in Asiatic hard clams in Hanoi was complex with multiple genotypes. Two worldwide epidemic genotypes GII.4 and GII.17 were identified in the present study, however, the dominant NoV genotypes were GI.5 and GII.3.

Aims: Norovirus (NoV) is a common foodborne virus in bivalve molluscs. This study aimed to identify genotypes of NoV genogroups I and II (GI and GII) in Asiatic hard clam (Meretrix meretrix) marketed in Hanoi, Viet Nam, in 2016.

Methods: A total of 39 Asiatic hard clam samples positive for NoV GI and/or NoV GII was genotyped using nested RT-PCR targeting fragment spanning the ORF1/ORF2 overlap region. PCR products were sequenced using Sanger sequencing and phylogenetic analysis was carried out using MEGA 11 software.

Results: NoV genotyping has been successfully performed for 23 samples. For NoV GI, four genotypes were detected: GI.2 (13.3%), GI.5 (46.7%), GI.6 (33.3%) and GI.8 (6.7%). We found five distinct genotypes of NoV GII, including GII.3 (61.1%), GII.4 (11.1%), GII.6 (11.1%), GII.13 (11.1%) and GII.17 (5.6%). Phylogenetic analysis revealed these NoV genotypes displayed high similarity with clinical strains circulating worldwide, especially strains from Asian countries.

Conclusions: The contamination of NoV GI and NoV GII in Asiatic hard clams in Hanoi was complex with multiple genotypes. Two worldwide epidemic genotypes GII.4 and GII.17 were identified in the present study, however, the dominant NoV genotypes were GI.5 and GII.3.