Risk factors for pneumonia in children infected with influenza A virus

Influenza A is an acute respiratory infectious disease caused by influenza A virus (IAV). Most patients recover spontaneously, but children face elevated risks of severe influenza manifestations. Pneumonia, a major complication of IAV infection, significantly impacts prognosis. Its atypical clinical presentation and rapid progression often lead to severe outcomes, threatening pediatric health. Early diagnosis and active treatment during disease progression are clinically critical.We retrospectively analyzed clinical data and laboratory results from pediatric inpatients with influenza A infection at Huzhou First People's Hospital (influenza sentinel hospital; March 2023–February 2025) to explore clinical characteristics and pneumonia risk factors.Among 195 children, 91 (46.67%) developed pneumonia. The pneumonia group exhibited longer symptom-to-visit intervals and higher rates of cough, expectoration, asthma, and dyspnea (P<0.05), but lower nasal discharge and antiviral treatment ≤48h rates. Laboratory results showed elevated L%, lymphocyte count, PLT, C3, C4, and LMR, yet reduced N%, NLR, PLR, and SII in pneumonia cases (P<0.05). Multivariate analysis identified Expectoration, elevated C3 and LMR are pneumonia risk factors; nasal discharge and antiviral treatment ≤48h are protective. Children infected with influenza A exhibiting expectoration without nasal discharge, lack of antiviral treatment within 48 hours, and elevated complement C3 and LMR levels require close monitoring for pneumonia development.