Molecular Characterization and Epidemiology of Human Noroviruses in the Sverdlovsk Region, Russian Federation.

Human noroviruses (HuNoVs) stand as the primary cause of acute viral gastroenteritis outbreaks worldwide, particularly impacting children under the age of five. In Russia, reports of norovirus gastroenteritis have surged, especially in the post-COVID-19 era starting in 2022, with elevated infection rates reported into 2024. These viruses exhibit significant mutational variability, leading to the emergence of recombinant strains that can evade immune responses. A comprehensive examination of the complete genome is crucial for understanding the evolution of norovirus genes and for predicting potential outbreaks. This research focuses on analyzing the genotypic composition of HuNoVs circulating in the Sverdlovsk region during 2024, using Sanger sequencing and next-generation sequencing (NGS). Biological samples were collected (n = 384) from patients diagnosed with norovirus infection within the region. Bioinformatics analysis targeted the nucleotide sequences of the ORF1/ORF2 fragment and the assembly of complete genomes for the GII.4 and GII.7 genotypes. In total, 220 HuNoVs were characterized, representing 57.3% of the collected samples. The main capsid variants forming the predominant genotypic profile included GII.4 (n = 88, 40%), GII.7 (n = 86, 39%), and GII.17 (n = 14, 6%). Using NGS, we successfully assembled 8 out of 10 complete genomes for noroviruses GII.4[P16] and GII.7[P7]. Non-synonymous substitutions appeared at amino acid sites corresponding to the subdomains of VP1 in these strains. This molecular-genetic analysis provides contemporary insights into the genotypic composition, circulation patterns, and evolutionary dynamics associated with the dominant genovariants GII.4[P16] and GII.7[P7].