Clinical, Molecular and Evolutionary Characterization of Noroviruses in Hospitalized Children With Acute...

Following rotavirus vaccine implementation in Vietnam, norovirus has gradually become equally an important as a cause of acute gastroenteritis (AGE) in children as rotavirus. This study aimed to investigate the genotype distribution and compare clinical manifestations of norovirus of children < 5 years of age hospitalized with AGE from 2016 to 2021. Of 6,718 specimens collected through active surveillance from 12/2016 to 05/2021, 2,317 (34.5%) were randomly selected for norovirus testing. Among the 477 (20.6%) norovirus-positive specimens identified from the previous surveillance, 390 (81.8%) were successfully genotyped for both partial RdRp and VP1 genes using online typing tools and 47 were selected for whole-genome sequencing. Overall, norovirus genogroup-II (GII) viruses dominated (97.3%) followed by GI (2.5%) and dual GI/GII infections (0.2%), with GII.4Sydney[P16] as the predominant genotype (51.5%) followed by GII.3[P12] (23.9%). Children infected with GII.4Sydney more commonly presented with thirst (65.8% vs 53.7%, p < 0.05) and showed a trend toward higher rates of sunken eyes compared with other genotypes (48.1% vs 38.1%, p = 0.053). A shift in predominant strain from GII.4Sydney[P31] viruses (50.8%) in 2016-2017 to GII.4-Sydney[P16] (51.9%-68.9% in 2018-2021) was observed. Two cases in 2017 were typed as GII.4Hong Kong[P31]. Compared to GII.4 Sydney[P31], GII.4Hong Kong had 12 amino acid substitutions in the P1-P2 domains. This study highlights the evolving genetic diversity of norovirus genotypes in Vietnam. The shift of the predominant strain from GII.4Sydney[P31] to GII.4Sydney[P16] in 2018 and detection of GII.4 Hong Kong[P31] in 2017 emphasizes the need for continuous molecular surveillance to inform public health prevention strategies.