Objective To understand the pathogen spectrum and epidemiological characteristics of viral diarrhoea in Qingdao, Shandong province, during 2023-2024 and provide data support for the effective prevention and control of viral diarrhoea.

Methods A total of 619 stool samples were collected from diarrhoea patients in 4 grade III hospitals in Qingdao. By nucleic acid extraction, rotavirus A, norovirus GⅠ/GⅡ, adenovirus, astrovirus, parechoviruss, and Sapovirus, were detected with fluorescence quantitative RT-PCR. For the positive samples, target gene amplifications and bi-directional sequencing were performed, and the genotypes were determined by BLAST comparison.

Results In thye 619 stool samples, 31.99% were positive for viruses (185/619), of which 13 were multi virus positive (2.10%). The detection rate was 8.89% for norovirus (55/619), 12.12% for rotavirus (75/619), 6.62% for adenovirus (41/619), 1.62% for astrovirus (10/619), 1.94% for human parechovirus (12/619), and 0.81% for Sapovirus (5/619). The incidences of norovirus, rotavirus and adenovirus infections showed obvious seasonality, with more infections occurring in winter and spring. In all the age groups, the infection incidence was highest in age group 0-<4 years. Genotyping analysis showed that norovirus GII.4, rotavirus G8P8, adenovirus C2 and F41, astrovirus 1, human parechovirus 1A and Sapovirus GII (GII.8 and GII.NA) were predominant.

Conclusion During 2023-2024, rotavirus and norovirus were the main pathogens causingviral diarrhoea in Qingdao. The infections showed obvious seasonality, mainly occurring in winter and sprin, and age distribution, mainly occurring in age group 0-<4 years. It is suggested to strengthen the active immunization of rotavirus and norovirus in infants and children aged 0-<4 years and the public health interventions in winter and spring to reduce the risk for virus transmission.