Epidemiology and clinical outcomes of common respiratory viruses detected by multiplex RT-PCR in patients at a national infectious disease reference center in Romania, 2022–2025

INTRODUCTION: A broad range of common respiratory viruses contributes substantially to the burden of acute respiratory infections (ARIs) across all age groups. However, data on their epidemiology, seasonality, and clinical impact in Eastern Europe remain limited. METHODS: We conducted a retrospective laboratory-based surveillance study including patients evaluated for ARIs at the National Institute for Infectious Diseases "Prof. Dr. Matei Balș", Bucharest, Romania, between November 2022 and October 2025. Respiratory samples were tested using multiplex real-time RT-PCR panels detecting multiple respiratory viruses. The present analysis focused on adenovirus (AdV), enterovirus (HEV), rhinovirus (HRV), parainfluenza virus (PIV), human coronaviruses (CoV), human bocavirus (HBoV), and human metapneumovirus (MPV). Epidemiological characteristics, detection patterns, and clinical outcomes were analyzed. RESULTS: Among 4930 patients tested, 1709 (34.7%) had at least one of the studied viruses detected, corresponding to 2144 viral detections (22.2% patients with viral codetections). HRV was the most frequently detected virus. Also, viral codetections most commonly involved HRV. Analysis of monthly detections across the three seasons studied demonstrated virus-specific temporal patterns. Specifically, MPV demonstrated a more consistent winter-spring detection pattern, whereas HRV was detected throughout the study period. Overall, 50.2% of patients required hospitalization, with the highest rates observed among patients with CoVs and MPV detection. Requirement of supplemental oxygen was more common in patients hospitalized with MPV (28.4%) and PIV (24.6%). Patients with viral codetections had higher hospitalization rates compared with those with monodetections (57.7% vs. 48.1%; OR = 1.47; p < 0.001), although no significant differences were observed in requirement of supplemental oxygen, ICU admission, or length of hospital stay. CONCLUSIONS: AdV, HEV, MPV, PIV, HBoV, CoV and HRV accounted for a substantial proportion of viral detections among patients evaluated for ARIs in routine clinical practice. The predominance of HRV and the frequent occurrence of viral codetections highlight the complexity of respiratory viral epidemiology revealed by multiplex molecular diagnostics. Broader surveillance of respiratory viruses may improve understanding of respiratory infection dynamics in the post-pandemic period.