Objective  To understand the molecular epidemiological characteristics of viral gastroenteritis in pediatric inpatients under five years old in Shanghai and provide scientific evidence for the prevention and control of viral diarrhea and the development and application of vaccines.

  Methods  Stool samples were collected from the inpatients aged ＜5 years due to acute gastroenteritis in a pediatric hospital in Shanghai, while epidemiological data were also collected. Laboratory tests, such as ELISA, real-time PCR and nested PCR, were performed to detect rotavirus, calicivirus, including norovirus and sapovirus, astrovirus and adenovirus.

  Results  A total of 805 stool samples were collected from 543 boys and 262 girls, the virus positive detection rate was 47.33%. Calicivirus and rotavirus A were the top two most common viruses, with a detection rate of 31.18% and 17.64% respectively. Norovirus GⅡ accounted for the largest percentage in calicivirus (95.62%). For rotavirus, the predominant genotype was G9P［8］(90.85%). While for norovirus GⅡ, GⅡ.4［P31］ and GⅡ.3［P12］ were the most common genotypes, accounting for 32.08% and 19.58% respectively. However since 2020 the detection rates of emerging genotypes GⅡ.4［P16］ and GⅡ.2［P16］ have increased significantly compared with 2018 and 2019 (χ²=17.337, P＜0.001, χ²=11.044, P=0.001 ). In addition, a RotaTeq vaccine strain of rotavirus was detected for the first time from the stool sample of a 4-month-old child.

  Conclusion  The tendency of higher detection rate of calicivirus than rotavirus was more obvious, indicating that the development and marketing of calicivirus (mainly norovirus) vaccine are more urgent. For the first time, the study revealed the main circulating and emerging genotypes of norovirus GⅡ in hospitalized children, providing references for the development of multivalent norovirus vaccine. In addition, the recent increase in detection rates of rotavirus G9 also suggested the necessity of continuous vigilance and more in-depth follow-up studies on the genotypic changes of rotavirus.