Objective: Influenza-like illness (ILI) is a major cause of hospitalization during respiratory virus seasons. This study aimed to investigate the pathogens detected in patients presenting with ILI symptoms and to analyze the results in conjunction with clinical, laboratory, and radiological findings.
Materials and Methods: This retrospective, single-center study included 446 hospitalized adults with ILI between epidemiological week 40 of 2024 and week 20 of 2025. Respiratory pathogens were identified using a multiplex real-time PCR assay detecting 18 viral and 5 bacterial pathogens. Demographic, clinical, laboratory, and radiological data were retrieved from electronic medical records. Disease severity was assessed using the CURB-65 score. Patients with Streptococcus pneumoniae detected by PCR were further evaluated according to radiological evidence of pneumonia.
Results: At least one respiratory pathogen was detected in 184/446 patients (41.2%), whereas no pathogen was identified in 262 patients (58.8%). The most frequently detected pathogens were S. pneumoniae, influenza viruses, and seasonal coronaviruses. The most common coinfection was influenza A plus S. pneumoniae. Among patients with pneumococcal PCR positivity, those with radiologically confirmed pneumonia were significantly older, had higher CURB-65 scores, and more frequently had concomitant influenza infection than patients without radiological evidence of pneumonia.
Conclusion: Multiplex molecular assays provide valuable information for respiratory pathogen detection, but molecular results, especially for bacterial pathogens such as S. pneumoniae, should be interpreted together with clinical and radiological findings.