Surveillance of human Group A rotavirus in Ningxia, China (2015-2021): Emergence and prevalence of G9P[8]-E2 and G3P[8]-E2 genotypes

Background: Group A rotaviruses (RVA) are the primary pathogens of acute gastroenteritis. Currently, two live attenuated RVA vaccines, LLR and RotaTeq, have been introduced into mainland China but are not included in the national immunization program. Because of the unknown genetic evolution of group A rotavirus in an all-age population in Ningxia, China, we monitored the epidemiological characteristics and circulating genotypes of RVA as a reference for developing vaccine strategies.Methods: We conducted seven years of consecutive surveillance of RVA based on stool samples from patients with acute gastroenteritis in sentinel hospitals in Ningxia, China, from 2015 to 2021. Reverse transcription quanti-tative polymerase chain reaction(RT-qPCR) was used to detect RVA in stool samples. Genotyping and phylo-genetic analysis of VP7, VP4 and NSP4 genes were performed by reverse transcription-polymerase chain reaction (RT-PCR) and nucleotide sequence determination.Results: RVA was detected in 16.58% (1436/8662) of 8662 stool samples. The positive rates were 7.17% (201/ 2805) and 21.09% (1235/5857) in adults and children, respectively. The most affected age group was infants and children aged 12-23 months, with a positive rate of 29.53% (p < 0.05). A significant winter/spring seasonality was observed. 23.29% positive rate in 2020 was the highest in 7 years (p < 0.05). The region with the highest positive rate in the adult group was Yinchuan, and the children's group was Guyuan. A total of 9 genotype combinations were found to be distributed in Ningxia. The dominant genotype combinations in this region gradually changed from G9P[8]-E1, G3P[8]-E1, G1P[8]-E1 to G9P[8]-E1, G9P[8]-E2, and G3P[8]-E2 during these seven years. Rare strains (e.g., G9P[4]-E1, G3P[9]-E3 and G1P[8]-E2) were occasionally detected during the study.Conclusions: During the study period, changes in the significant RVA circulating genotype combinations and the emergence of reassortment strains were observed, particularly the emergence and prevalence of G9P[8]-E2, G3P [8]-E2 reassortants in the region. These results indicate the importance of continuous monitoring of the mo-lecular evolution and recombination characteristics of RVA, and should not be limited to G/P genotyping but should consider multi-gene fragment co-analysis and whole genome sequencing.