Risk Factors for Influenza Virus Related Severe Lower Respiratory Tract Infection in Children

Background: Influenza virus is one of the most common respiratory pathogens for all age groups and may cause seasonal outbreaks. Our aim was to identify risk groups and factors associated with severe clinical course including mortality in children with influenza-related lower respiratory tract infection (LRTI). Methods: We conducted a retrospective study in children hospitalized with influenza virus LRTI from 2008 to 2018. Data on demographic features, influenza type, viral coinfection, primary and secondary bacterial infections (SBIs), time of onset of antiviral treatment, comorbidities, hospitalization length, pediatric intensive care unit admission/invasive mechanical ventilation (IMV) need and mortality were collected from medical records. Results: There were 280 patients hospitalized with LRTI and median hospitalization length was 9 days. Congenital heart disease, neuromuscular disease, SBIs and late-onset antiviral treatment were independent risk factors for prolonged hospital stay (P < 0.05). Pediatric intensive care unit admission was present in 20.4% (57) of the patients and 17.1% (48) of all patients required IMV. SBIs, lymphopenia, neutrophilia, immunosuppression and human bocavirus coinfection were independent risk factors for IMV support (P < 0.05). Eighteen patients died and immunosuppression, lymphopenia and SBIs were independent risk factors for mortality (P < 0.05). Conclusions: Presence of comorbidity, SBIs, neutrophilia and lymphopenia at admission identified as risk factors for severe influenza infections including need for IMV and death. Although several studies showed that antiviral treatment reduce hospitalization, complications and mortality, there is a lack of prospective trials and patients for antiviral therapy should be carefully chosen by the clinician.