Influenza as the Predominant Cause of Severe Hepatic Involvement in Children Hospitalized with Acute Respiratory Infections: A Post-COVID-19 Era Analysis

Background: Following the coronavirus disease 2019 (COVID-19) pandemic, increased reports of severe acute hepatitis of unknown etiology in children have raised concerns about virus-associated liver injury. Acute respiratory tract infections (ARTIs) are a common cause of pediatric hospitalization and may be accompanied by reactive hepatitis; however, virus-specific patterns of hepatic involvement remain incompletely defined. This study aimed to evaluate liver involvement associated with ARTIs in hospitalized children. Methods: This retrospective study included pediatric patients (<18 years) hospitalized with ARTIs between October 2021 and May 2023. Respiratory viruses were identified via multiplex real-time polymerase chain reaction assays. Liver function tests were systematically evaluated during hospitalization. Transaminase elevations were categorized according to the upper limit of normal (ULN = 40 U/L). Acute hepatic failure was defined according to the Pediatric Acute Liver Failure criteria. Results: A total of 179 patients were analyzed (median age: 38 months; 59.2% male). Elevated AST and ALT levels were observed in 24.0% and 8.4% of patients, respectively. Adenovirus was the most frequently detected virus (11.2%), followed by influenza A (7.3%) and parainfluenza virus (6.7%). Severe transaminase elevations (>5 × ULN and >500 U/L) were observed in patients with influenza infection. All cases of acute hepatic failure (n = 3) were associated with influenza infection. Other respiratory viruses were associated with mild or transient liver enzyme abnormalities. Conclusions: Severe hepatic involvement—including severe transaminase elevation and acute hepatic failure—occurred exclusively in children with influenza infection, particularly influenza B, while mild and transient liver enzyme abnormalities were common across other respiratory viral infections. These findings highlight the importance of targeted liver function monitoring in pediatric influenza patients and provide clinically relevant data on virus-specific hepatic involvement in the post-COVID-19 era.