Detection of a novel recombinant norovirus from sewage water in toyama prefecture, Japan.

Recently, the recombination event of norovirus (NoV) has been reported with high frequency, suggesting that RNA recombination is a major driving force in NoV evolution. To assess the incidence of NoV recombination in a residential area, we conducted a molecular biological survey of NoVs existing in sewage water in Toyama Prefecture, Japan. Although GII/4 was predominantly detected in sewage water that was associated with a high frequency of outbreaks caused by this genotype, other genotypes, including two types of recombinant strain, were identified during the survey period. One of the recombinants is the WUG1 type, which was first detected in Saitama Prefecture in 2000. The other recombinant is a novel type derived from two parent strains of genogroup II, GII/7 for the RNA-dependent RNA polymerase and GII/13 for the capsid. This suggests that certain NoVs circulating in the area are occasionally changing their genetic properties by recombination events.