Prevalence and associated factors of pneumococcal carriage among children with respiratory viral infections in Türkiye.

INTRODUCTION: The interaction between nasopharyngeal pneumococcal carriage (NPC) and respiratory viral infections (RVI) is poorly understood. This study aimed to investigate the prevalence and epidemiology of NPC, and its correlation with RVI. METHODOLOGY: This retrospective study included patients aged < 18 years who presented with RVI symptoms between 1 February and 30 June 2023. Naso-oropharyngeal swabs were tested using quantitative polymerase chain reaction (PCR) for Streptococcus pneumoniae and respiratory viruses. Patients were grouped by NPC status and compared for viral detection, and clinical and demographic characteristics. RESULTS: NPC was detected in 15.7% (n = 1,185) of the 7,522 samples analyzed. The mean age was 56.5 ± 49.3 months, being significantly lower in NPC-positive patients (p < 0.001). Most (82%) were fully vaccinated against pneumococcus; 16% had underlying conditions. The most frequent viruses were adenovirus (17.2%), influenza B (9.0%), severe acute respiratory syndrome coronavirus 2 (5.3%), respiratory syncytial virus (4.9%), and influenza A (2.8%). Adenovirus (19.7%) and influenza B (11.0%) were significantly more frequent in NPC-positive patients than in NPC-negative patients (p < 0.001 for both). Overall, 20.5% were hospitalized, and 2.4% required intensive care. Intensive care admission was higher among NPC-positive patients, whereas mortality did not differ. CONCLUSIONS: NPC was epidemiologically associated with the detection of certain respiratory viruses, particularly adenovirus and influenza B. Given the retrospective design and lack of pneumococcal serotype data, these findings should be interpreted as associations rather than evidence of causality. Further prospective studies are warranted to clarify the bacterial-viral interactions and their clinical relevance.