Note: *untypeable Supplement 1. A quarterly distribution of G and P type combinations detected in Vietnam, Year Grand Total Genotype Jan- Mar Apr-JunJul-SepOct-Dec Yearly Total Jan-MarApr-JunJul-SepOct-Dec Yearly Total Jan-MarApr-JunJul-SepOct-Dec Yearly Total Jan-MarApr-Jun Half- yearly Total G1P[8] G2P[4] G8P[8] G3P[8] Others G1+G8P[8] G2+G8P[8] G2+G8P[4]+P[8] G1+G2+G8P[4]+P[8] Other Mixed UT*

Wa RVN RVN RVN RVN KUN Wa KUN RVN RVN RVN RVN RVN RVN RVN RVN RVN RVN RVN RVN RVN RVN RVN RVN RVN Supplement 2

Supplement 2. Electrophoretic migration pattern of genomic double-stranded RNA of Vietnamese G8P[8] RVA strains detected between October 2014 and May 2015 alongside Wa (long RNA pattern) and KUN (short RNA pattern) as positive controls on 10% polyacrylamide gel stained with silver nitrate. Strain names are indicated at the top of each lane on the gel while numbers on the left side represent the genome segment number. All specimens possessed short RNA patterns almost indistinguishable from each other. Strain RVN was detected the earliest and possessed the predominant electropherotype.

Supplement 3

Supplement 3. A maximum clade credibility tree of VP7 nucleotide sequences of eight Vietnamese G8P[8] strains and the other closely related G8 strains within lineage IV (Fig. 1). The analysis was conducted using the Bayesian Markov chain Monte Carlo framework implemented in BEAST software package v.1.8.1; the TN93 + G substitution model, a coalescent constant size tree prior and a lognormal relaxed clock model were assumed for the analysis. Two independent runs were carried out for twenty million generations and assessed with the Tracer software v.1.6 ( The tree was annotated with a TreeAnnotator and viewed in FigTree software v (