Two novel noroviruses and a novel norovirus genogroup in California sea lions.

In this study, two novel noroviruses (NoVs) were discovered from faecal samples from California sea lions from an oceanarium in Hong Kong, and named California sea lion NoV 1 (Csl/NoV1) and California sea lion NoV 2 (Csl/NoV2). Whole-genome sequencing showed that the genome organization and amino acid motifs of both Csl/NoV1 and Csl/NoV2 were typical of those of other NoVs in their open reading frames (ORFs). Csl/NoV1 possessed only 52.6-52.8 % amino acid identity in VP1 to the closest matches in genogroup GII. Therefore, Csl/NoV1 should constitute a novel genogroup of NoV. Shifting of the phylogenetic position of Csl/NoV1 in the RdRp, VP1 and VP2 trees was observed, which may have been due to recombination events and/or biased mutations. Csl/NoV2 possessed 55.4-56.2 % amino acid identity in VP1 to its closest relatives in genogroup GVI, which means that it represents a new genotype in genogroup GVI. Further studies will reveal what diseases these NoVs can cause in marine mammals.