Fig. 3

Phylogenetic analysis of GII.4 NoV strains detected in South China during the period from August 2015 to October 2017, based on the nucleotide sequences of the capsid P2 subdomain. Phylogeny was reconstructed using the maximum-likelihood method implemented in MEGA v7.0 [25] with the TN93 + G + I model (best nucleotide substitution model for the dataset based with the lowest Bayesian Information Criterion scores). Numbers at the nodes indicate supporting bootstrap values (%) for 1000 resampled datasets, and bootstrap values of selected branches are shown (> 70%). The scale bar represents the unit for the expected number of substitutions per site. Local NoV strains from this study are labelled by red triangles (for strains in 2016 and 2017) and blue triangles (for strains in 2014 and 2015), respectively. Local NoV strains from previous studies are labelled by blue squares. Information of all reference sequences used for phylogenetic analysis in this figure was listed in the Additional file 1 Table S2