Abstract:Objective To investigate the epidemiological characteristics of infectious mononucleosis (IM) among hospitalized children in Hebei Children's Hospital. Methods From January 1, 2019 to December 31, 2022, medical information including gender, age, hospitalization cost, and hospital stay were extracted from the first page of the discharge medical record from Hebei Children's Hospital for analysis. Results A total of 1 043 IM cases were identified, accounting for 0.53% (1 043/197 706) of all hospitalized cases，and the male-to-female ratio was 1.56∶1. The hospital stay for all IM cases was 9 (7,11) days, and 41.42% and 58.58% of the 1 043 children were from urban and rural areas, respectively, with no statistically significant (P＞0.05). The hospitalization cost was 8 065 (715.60, 1 343.29) yuan. The proportion of IM children in all hospitalized children aged ＜1, 1-3, 4-6, 7-12 and 13-18 years old were 0.05%, 0.76%, 0.94%, 0.32% and 0.12%,respectively, and the difference was statistically significant (χ²=445.580,P＜0.01), with the highest in aged 4-6 years old. The proportion of IM children in all hospitalized children in 2019, 2020, 2021 and 2022 were 0.66%, 0.74%, 0.61% and 0.11%, respectively, with a statistically significant difference (χ²=232.145,P＜0.01), which increased first and then decreased, with the highest in 2020. In addition, the number of IM hospitalization reached the peak from July to September and the lowest from December to March. Common complications of hospitalized IM children included liver function abnormalities, bronchitis, and pneumonia. Conclusion The prevalence of IM in hospitalized children is characterized by age and seasonality, and measures should be taken to reduce the incidence of IM in children, and to reduce their disease burden and complications.