Objective:To conduct a nested case-control study based on the cohort of hospitalized children in provincial children's hospitals, and explore the influencing factors of infectious diarrhea (ID) in hospitalized children.Methods:Clinical data of hospitalized children admitted to the Department of Gastroenterology from June 2021 to June 2023 were collected. Using a combination of prospective and retrospective methods, the children were divided into a case group (n=326) and a control group (n=992) according to whether they were diagnosed with ID. Indicators between the two groups were compared to summarize the clinical characteristics of children with ID, analyze the influencing factors of ID occurrence, and analyze the etiological diagnosis results to compare the clinical characteristics of bacterial and viral ID.Results:There were 261 cases of bacterial infection, 107 cases of viral infection, and 42 cases of mixed infection, mainly including 139 cases of salmonella enteritis, 93 cases of bacterial intestinal infection, and 72 cases of rotavirus enteritis. All children with ID had diarrhea of varying degrees, and some were accompanied by symptoms such as fever, nausea/vomiting. The age of the children was mainly under 5 years old, and there was no statistically significant difference in age distribution between different genders (χ²=2.096, P=0.351). The incidence of ID showed a seasonal distribution, with a high incidence in summer and autumn, especially from June to August. Univariate analysis showed that there were statistically significant differences between the two groups in terms of hygiene habits, dietary status, and living conditions (P<0.05); Logistic regression analysis showed that the above factors were all independent risk factors for ID occurrence (P<0.05). The distribution of pathogens was dominated by bacteria (80.06%), followed by viruses (19.93%), and the main pathogens were Salmonella and rotavirus.Conclusion:The incidence of ID in children has a seasonal peak, with a slightly higher number of males. The main pathogens are Salmonella and rotavirus. Poor hygiene habits, diet, and living conditions can increase the risk of ID, so targeted prevention and control should be strengthened.