The predominance of recombinant Norovirus GII.4Sydney[P16] strains in children less than 5 years of age with acute gastroenteritis in Tehran, Iran, 2021–2022.

• The RdRp and VP1-based dual typing by genetic analysis of circulating NoVs in Iran. • GII.4 Sydney_2012[P16] was determined as the most common strain. • GII.8[P8] viruses were also found to be as the second most common. The present study was aimed to both detect emerging noroviruses and investigate RdRp and VP1-based dual typing of circulating noroviruses in hospitalized children less than 5 years of age with acute gastroenteritis (AGE) in Iran. For this purpose, a total of 200 stool specimens were screened during 2021–2022 by real-time RT-PCR for genogroup I and II (GI and GII) and dual-typed by sequence analysis of PCR products, using a web-based norovirus Typing Tool and phylogenetic analysis. The GI and GII noroviruses were detected in 20% of 200 specimens. The GII.4 norovirus was found to be the most common VP1 genotype (53%) followed by GII.8 (32%), GII.7 (6%), GII.17 (6%), and GII.3 (3%). The GII.P16 norovirus was also found as the predominant RdRp type (53%) followed by GII.P8 (32%), GII.P7 (6%), GII.P17 (6%), and GII.P31 (3%). To our knowledge, this is the first report that highlights the dominancy of recombinant norovirus GII.4Sydney[P16] and newly emerging of norovirus GII.8 [P8], GII.17 [P17] and GII.3 [P16] in Iran. These findings further indicate inter-genotype recombinant strains of noroviruses. [ABSTRACT FROM AUTHOR]