Phylogenetic tree of the partial VP1 (ORF2, 1,560 nt) in environmental samples determined by the maximum likelihood method.

<p>The VP1 nucleotide sequences of noroviruses harvested from the study area are indicated as closed squares (■). The sampling site numbers are shown next to each sample label. The percentages of trees in which the associated taxa clustered together are shown next to the branches (bootstrap values of ≥95 are shown). The tree is drawn to scale with branch lengths measured in the number of substitutions per site. Each sample label number on the tree indicates the sampling date (e.g., 20150321 = March 21, 2015). An outgroup reference strain (GI.1; GenBank ID: M87661) is not shown in this figure.