High Prevalence of Typical Human Wa-Like G3P[8] Rotavirus Strains in Children Hospitalized With Acute Gastroenteritis in Thailand, 2022-2023.

Rotavirus Group A (RVA) infection is a significant cause of acute gastroenteritis in children. This study aimed to characterize RVA in Chiang Rai, Thailand, from 2022 to 2023. A total of 274 fecal samples were tested for RVA by RT-PCR. RVA was detected in 9.9% (27/274). The predominant RVA genotype was typical human G3P[8] (26/27, 96.3%), followed by G4P[6] (1/27, 3.7%). The highest infection rate was observed in children under 5 years of age (25/27, 92.6%). RVA was widespread with a single peak extending from winter to summer. Phylogenetic analysis revealed two lineages of G3P[8] strains circulating in Thailand: the typical human G3P[8] and the equine-like G3P[8]. The G3P[8] strains in this study had aspartic acid (D) at position 221, whereas previously reported G3P[8] strains had alanine (A). These G3P[8] strains had a Wa-like backbone: G3-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 constellation. G3P[8] strains also carried some amino acid differences in the antigenic epitopes comparted to vaccine strains. Homology models of the VP7 and VP8* proteins confirmed that these differences were on the surface-exposed region of the outer capsid structure. It is of interest whether these typical human G3P[8] strains will emerge in the future and replace other genotypes.