Re-emergence and Spread of Norovirus Genotype Gii.17 Variant C in 2021-2023

Abstract

Norovirus is one of the leading causes of acute gastroenteritis worldwide and is characterized by significant genetic diversity. In this study, based on phylogenetic analysis of the genome sequences of noroviruses circulating in Nizhny Novgorod in 2014–2023, as well as those retrieved from the GenBank database, the return to active circulation of the C variant of the GII.17[P17] genotype, displaced in 2015–2016 by the D variant, is shown. A new subvariant C2, different from the C1 subvariant circulating in the middle of the last decade, was identified. Amino acid substitutions characteristic of C2 were found in the main structural protein VP1, bringing it closer to the Tokyo_JP_1976 strain identified in the 1970s. It was established that the C2 subvariant circulated in 2021–2023 in European and American countries and caused outbreaks of norovirus infection. The data obtained indicate that the evolution of the phylogenetic lineage represented by the C variant of the GII.17 genotype has been continuing in the last decade and has the character of convergence with the ancestral strain, and for four years (2017–2020) these processes were latent.