Full-genomic analysis of a human norovirus recombinant GII.12/13 novel strain isolated from South Korea.

Norovirus (NoV) genogroups I and II are frequently recognized as the main causes of acute gastroenteritis and outbreaks of non-bacterial foodborne diseases. Furthermore, variants and recombinant strains of this virus are continuously emerging worldwide. The aim of this study was to identify NoV strains and to investigate and characterize rare genotypes. Stool samples (n = 500) were collected from patients with symptoms of acute gastroenteritis in Korea between December 2004 and November 2007. For analysis of the samples, rapid genotype screening was performed using reverse transcriptase-polymerase chain reaction. Full sequencing, using a newly designed set of 12 primers, revealed GII-12/13 strain. The partial sequence of GII-12/13 strain was compared with published NoV (GII-1 - 14) sequences targeting RdRp and capsid regions using phylogenetic analysis with the SimPlot program, which could evaluate recombination breakpoints. SimPlot analysis was also performed with the strain GII-12/Gifu-96/JPN (AB045603) for the RdRp region and with GII-13/G5175B-83/AUS(DQ379714) for the capsid region. NoV was detected in 19 of the 500 stool samples (3.8%). Genogroup GII-4 was found most frequently (n = 9, 1.8%), followed by GII-3 (n = 4, 0.8%), GII-6 (n = 3, 0.6%), GI-6 (n = 2, 0.4%), and GII-12/13 (n = 1, 0.2%). Importantly, we identified a novel NoV recombinant strain, C9-439 (KF289337), indicating potential risks, which suggested that, recombination occurred in the region between open reading frames 1 and 2 of the GII-12/13 strain and that breakpoints occurred in the polymerase region.