Impact of demographic, clinical, and viral factors on severe influenza in young children in Fuzhou

Background Identify risk factors for severe influenza in children under 5 years of age in the Fuzhou region to provide evidence-based support for early identification of high-risk patients, optimization of Pediatric Intensive Care Unit (PICU) resource allocation, and development of targeted intervention strategies. Methods A total of 386 severe influenza cases and 1,544 non-severe cases among children under 5 years old in Fuzhou City were collected from January 2015 to January 2025. The non-severe cases were matched for the same period, same region, parental education level, and age (±1 year). A retrospective case–control study design was employed to analyze demographic characteristics, clinical symptoms, laboratory indicators, medical history, and viral subtypes between the two groups. Multivariate logistic regression analysis was used to identify independent risk factors for severe influenza. Results Multivariate analysis revealed that male gender, children living in dispersed communities, obesity, rural residence, lack of influenza vaccination, time from onset to presentation >2 days, time from onset to antiviral treatment >2 days, persistent high fever >3 days, tachypnea/dyspnea, altered mental status/ convulsions, elevated neutrophil-to-lymphocyte ratio (NLR), high C-reactive protein (CRP) levels, low albumin levels, history of chronic respiratory disease, history of metabolic and endocrine disorders, and infection with influenza A (H1N1) virus were all risk factors for severe influenza in children under 5 years of age (all p < 0.05). The median recovery time in the severe group was 19 days, significantly longer than the 10 days in the non-severe group ( p < 0.001). Conclusion The occurrence of severe influenza in children under 5 years of age is influenced by multiple factors, including demographic characteristics, clinical features, laboratory indicators, past medical history, and viral subtype. Efforts should focus on strengthening prevention and control in key populations, increasing vaccination rates, optimizing the allocation of medical resources, and enhancing primary care capabilities to reduce the incidence of severe influenza in children and improve outcomes.