Prevalence of Enterovirus genus respiratory infections and co-infections: a cross-sectional study in a Northeast Italian Hospital (2023-2025)

Objectives: Enteroviruses (EV) are major causes of acute respiratory infections (ARIs), but their epidemiology and co-infection patterns in hospitals are not fully understood. We assessed EV prevalence, co-infections and seasonal distribution in patients attending a hospital in northeast Italy over three years. Methods: We performed a retrospective cross-sectional study from January 2023 to December 2025. Patients with influenza-like illness or ARIs were tested using a multiplex respiratory panel. Demographic, temporal and laboratory data were analysed to evaluate associations between EV detection, age, gender, season and infection type (single vs. co-infection). Results: Among 3,444 respiratory samples from 3,154 patients, 2,168 (62.9%) were positive for at least one pathogen. EV was the most frequently detected pathogen (47.6%). Most infections occurred in children ≤17 years (84.6%), especially those aged 0-4 years. Co-infections were identified in 45.7% of EV-positive cases, mainly with adenoviruses (38.0%) and Mycoplasma pneumoniae (8.1%). EV circulated year-round, with single infections peaking in autumn and co-infections in spring. Single infections were associated with older pediatric age groups and autumn, while co-infections were linked to younger children and spring. Conclusions: EV are leading respiratory pathogens in this setting, particularly in young children, supporting multiplex diagnostics and continuous surveillance.