1 INTRODUCTION
Acute gastroenteritis (AGE) has been identified as the second leading cause of death in children <5 years of age, causing approximately 500,000 deaths annually worldwide 1. Group A rotavirus (RVA) is the most common cause of AGE in young children especially under five years of age worldwide2,3. As the main pathogen of AGE, RVA infection and death occur in all countries worldwide, but mainly in developing countries 4,5. Based on the Global Burden of Disease 2019 Study (GBD 2019), RVA caused a higher death burden in African, Oceanian, and South Asian countries in the past three decades6.
Rotavirus was first discovered in 1973 by Bishop and her colleagues in duodenal biopsies of children with AGE 7. Rotavirus is a non-enveloped RNA virus of the family Reoviridae in the subfamily Sedoreovirinae , belonging to the genusRotavirus , with a spherical shape and size of 70 nm. It consists of a genome of 11 segments of double-stranded RNA (dsRNA) surrounded by a three-layered icosahedral protein envelope 8. The genome segments encode six structural viral proteins (VP1-4, VP6 and VP7) and six non-structural proteins (NSP1-5/6). The two outer capsid proteins, VP7 (glycoprotein) and VP4 (protease-sensitive protein) contain neutralizing epitopes and induce protective immunity. The middle layer consists of VP6, while the inner layer is formed by VP2, which encloses two proteins, VP1 and VP3 5. Based on the antigenicity of the VP6 protein, ten RV groups (A-J) and two new tentative groups (K and L) have been documented. RVA are by far the most important species in the world in clinical and epidemiological terms9-12. RVA is further subdivided into G and P genotypes based on VP7 and VP4, respectively 8. Currently, about 42 G genotypes and 58 P genotypes have been reported to the Rotavirus Classification Working Group (RCWG) (https://rega.kuleuven.be/cev/viralmetagenomics/virus-classification/rcwg)13. Among these, several genotype combinations, including G1P[8], G2P[4], G3P[8], G4P[8], G9P[8] and G12P[8], together account for an estimated 90-95% of all RVA infections worldwide8,14-16. In contrast to high-income countries, there is a wide diversity of RVA strains in African countries, where atypical RVA, including the G1P[4], G1P[6], G8P[4], G8P[8] and G6P[6] genotypes, are also commonly characterized8.
Vaccination is considered the primary public health approach to control RVA infection and reduce associated morbidity and mortality3,17-19. Currently, two live-attenuated vaccines, monovalent Rotarix and pentavalent RotaTaq, are available for global use. Two Indian-manufactured vaccines, monovalent Rotavac and pentavalent Rotasiil, were recently prequalified by WHO in 201820. In China, two RVA vaccines have been licensed for the Chinese market: Lanzhou lamb RVA vaccine (LLR) consisting of RVA serotype G10P[12] (Lanzhou Institute of Biological Products) licensed in 2001, and RotaTeq developed from the bovine WC3 strain reassorted with human strains G1-G4 and P[8] (Merck) licensed in 2018 21. However, most children in China do not receive RVA vaccination in time due to the high additional cost of RVA vaccination 18. Given the diversity of RVA genotypes and the variety of RVA vaccines, long-term and continuous surveillance of the epidemiology of RVA is essential to provide implications to health authorities on suitable policies for RVA vaccination in children.
In Shanghai, studies on RVA infection in children with AGE during 2020 to 2022 were lacking 22. To better understand the role of RVA in children younger than 16 years with AGE in Shanghai, we determined the age distribution, gender distribution, seasonal pattern and genotypic distribution of RVA and updated the profiles of RVA genotypes from May 2020 to December 2022.