Research Information System
Medicine, vol.105, no.19, 2026 (SCI-Expanded, Scopus)
Seasonal influenza causes substantial morbidity and mortality worldwide, yet local multi-season data from middle income settings remain limited. This study aimed to assess the clinical burden of influenza hospitalization and identify the independent predictors of severe outcomes in adults in Türkiye. A multicenter active surveillance study was conducted across Global Influenza Hospital Surveillance Network sites in Türkiye over 9 influenza seasons (2012-2024). Patients screened within 72 hours of hospital admission with symptoms of influenza-like illness were included. Only adults with laboratory-confirmed influenza infection using real-time reverse transcription polymerase chain reaction were included in the risk analysis. Multivariate logistic regression was performed to identify independent risk factors for intensive care unit (ICU) admission, mechanical ventilation (MV), and in-hospital mortality. Among 2439 hospitalized adults; 351 had laboratory-confirmed influenza, of whom 85.2% had at least 2 chronic condition. Severe outcomes were frequent: 21.1% required intensive care, 21.1% required MV, and 11.1% died. Of those who died in the hospital, 69.2% were 65 years and older. Each additional year of age increased the odds of ICU admission by 3% and in-hospital death by 2%. Diabetes increased ICU admission risk (adjusted odds ratio [aOR] 1.91, 1.09-3.33). Chronic obstructive pulmonary disease was the only independent predictor of MV (aOR 3.13, 1.77-5.61). Patients with chronic kidney disease had a more than fourfold increased risk of in-hospital mortality (aOR 4.54, 2.05-9.88) and malignancy (aOR 3.75, 1.63-8.38) were another strongest determinant of mortality. Influenza vaccination reduced the risk of ICU admission by 66% (aOR 0.34, 0.12-0.80). These findings highlight the considerable burden of influenza among older adults and those with chronic conditions, reinforcing the need for enhanced vaccination strategies and timely antiviral treatment for this population.