Detection of Enteric Viruses in Fecal Specimens from Nonbacterial Foodborne Gastroenteritis Outbreaks in Tokyo, Japan between 1966 and 1983

We investigated the prevalence of 5 enteric viruses (norovirus [NoV], sapovirus, rotavirus, astrovirus, and adenovirus) in archived stool specimens collected from 70 foodborne gastroenteritis outbreaks in Tokyo, Japan, which occurred from 1966 to 1983, and genetically characterized these viruses. NoV was detected in 48 (68.6%) outbreaks, while SaV, group C rotavirus (RVC), and astrovirus were detected in 1 (1.4%) outbreak each. Based on the partial capsid sequences, the detected NoVs were classified into the following genotypes: 9 in genogroup I (GI; GI.1-6, GI.8, GI.9, and GI.NA), 13 GII (GII.1-9, GII.13, GII.16, GII.17, and GII.22), and one in GIV. The oldest NoV outbreaks occurred in 1966. No predominant genotype was found. One strain, classified as GI. NA based on the N/S region sequence, was subsequently classified as GI.8 based on the complete VP1 sequence. Nine types of recombinant NoV sequences, including 7 unreported combinations, were identified. Further genetic characterization of NoV GII.17 and GII.4 demonstrated that the NoV GII.17 strains detected from 1970 to 1982 clustered independently from previously reported NoV GII.17 strains. Phylogenetic analysis, using the complete VP1 region and the P2 domain, demonstrated that NoV GII.4 strains collected between 1975 and 1980 clustered with archival strains collected in the USA in the mid-1970s. In contrast, a NoV GII.4 strain collected in 1983 formed an independent branch from reference strains collected in the mid-1970s to 2012.