MOLECULAR-GENETIC ANALYSIS OF OUTBREAKS CAUSED BY NOROVIRUS IN SEVERAL CONSTITUENT ENTITIES OF THE FAR EASTERN FEDERAL DISTRICT DURING 2021–2025

Introduction. Norovirus causes acute gastroenteritis, primarily in children aged under 5 years and among the elderly, and frequently causes outbreaks in educational and healthcare institutions, summer recreation camps, on cruise liners. The current classification of noroviruses distinguishes 10 genogroups. Among them GII.4Sydney [P.16] и GII.17[P.17] are prevailing in recent years.

Objective of the current research was to conduct molecular-genetic analysis of norovirus genotypes causing outbreaks in several constituent entities of the Far Eastern federal district during 2021-2025.

Materials and methods. In order to establish norovirus genotypes, biological material was obtained from patients diagnosed with acute intestinal infections residing in the Khabarovsk krai, Amur oblast and Sakhalin oblast. Amplification of specific parts of genome and subsequent Sanger sequencing as well as phylogenetic analysis were performed to isolate norovirus nucleotide sequences and determine their genotype.

Results and discussion. Molecular-genetic investigation of acute intestinal infections outbreaks allowed to establish circulation of the following norovirus subtypes: GII.4Sydney [P.16], GII.17[P.17] и GII.7[P.7] – in the Khabarovsk krai, GII.7[P.7], GII.3[P.12] – in the Amur oblast and GII.2[P16] – in the Sakhalin oblast. A shift in prevailing norovirus genotypes responsible for outbreaks was observed. GII.2[P16], GII.12[P16], GII.14[P7] и GIX.1[GII.P15] norovirus types were identified in 2021. GII.4Sydney [P.16] и GII.17[P.17] were dominant genotypes in 2022. Phylogenetic analysis showed 5 variants of GII.4 Sydney norovirus genotype.

Conclusion. The diversity of norovirus genotypes, high possibility of re-emergence of the former strains with higher pathogenicity, demonstrates the necessity for ongoing surveillance over norovirus infection with integration of molecular-genetic methods. Considering the damage caused to the gastrointestinal tract, which is mainly observed in children of preschool age, particular attention should be paid to outbreaks in organized groups of children.

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