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 WUG I 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.