A31 Molecular characterization of circulating human noroviruses in Canada to assess RT-qPCR assays used for the detection of foodborne noroviruses

major (ORF2) and minor (ORF3) capsid proteins. Noroviruses are very diverse and among the three genogroups (GI, GII, and GIV) that infect humans,>30 genotypes have been described. One genotype (GII.4) causes>80 per cent of norovirus outbreaks worldwide, a new variant of this strain emerges every two to three years, rapidly replaces the circulating variant and then becomes dominant globally. A high mutation rate as well as recombination contributes to high diversity of noroviruses. From April 2009–May 2016, large-scale surveillance, based within the Rotavirus Sentinel Surveillance Programme in South Africa (SA), detected noroviruses in 12.9 per cent of children with severe diarrhoea. Norovirus infections were most frequently detected in children<2 years of age with spring/early summer seasonality. Norovirus genogroup II strains predominated (>80 per cent) and strains were genotyped based on partial RNA-dependent RNA polymerase (RdRp) and capsid nucleotide sequences. To date sixteen RdRp and twenty-two capsid-based genotypes have been identified with GII.4 the overall predominant strain (57 per cent) followed by GII.3. The combined RdRp/capsid genotype was determined for 333 GII strains. Fifteen confirmed recombinant norovirus strains circulated during the study period, including several novel recombinants. The GII.4 New Orleans 2009 variant predominated from 2009 to 2013 after which it was replaced with the GII.4 Sydney 2012 variant. In 2016, the capsid of the Sydney 2012 variant was detected with the GII.P16 RdRp in SA. Phylogenetic analysis based on the capsid gene (1,623 bp) of fifty-two GII.4 variants, circulating between 2009 and 2016, indicated that both pandemic strains (New Orleans 2009 and Sydney 2012) diversified in SA and several sub-clusters within these major variants were identified during the study. In addition, three minor GII.4 variants, restricted to SA were characterised. Continued norovirus surveillance in SA is essential to understand the epidemiology of this diverse group of viruses and to enable further studies on norovirus evolution.