Incidence and Clinical Characteristics of Hemorrhagic Manifestations in Children With Influenza: A Multicenter Retrospective Study

BACKGROUND AND OBJECTIVES: Hemorrhagic manifestations in pediatric influenza are poorly characterized, despite influenza being a leading cause of acute respiratory illness in children. We aimed to determine the incidence and clinical characteristics of hemorrhagic manifestations associated with influenza in children presenting to emergency departments, and to describe available laboratory findings. METHODS: We conducted a multicenter retrospective cohort study across 9 pediatric hospitals in Spain. Children 0-16 years of age with laboratory-confirmed influenza who presented to emergency departments during January-February 2024 and 2025 were included. Demographic characteristics, influenza virus type, hemorrhagic manifestations, available laboratory parameters and clinical outcomes were analyzed. RESULTS: Among 3363 children with influenza, 67.9% had influenza A virus infection and 32.0% influenza B virus infection. Median age increased from 3.4 years in 2024 to 4.9 years in 2025 (P < 0.001). Hemorrhagic manifestations occurred in 3.8% of cases, most commonly petechiae or purpura (2.3%) and epistaxis (1.5%). The incidence was higher in 2025 than in 2024 (4.4% vs. 2.4%; odds ratio 1.87, 95% confidence interval: 1.19-2.94). Blood tests were performed in 18.9% of patients. Among those tested, platelet counts differed modestly between children with and without hemorrhagic manifestations, although thrombocytopenia and coagulation parameters were not significantly associated with bleeding. Most patients (95.9%) were managed as outpatients, and hospitalizations due to hemorrhagic manifestations were rare. CONCLUSIONS: Hemorrhagic manifestations occur in approximately 4% of pediatric influenza cases presenting to emergency departments and are generally mild and self-limited. They are not associated with consistent or clinically relevant laboratory abnormalities, supporting the concept of a transient and multifactorial disturbance of hemostasis during influenza infection.