Background: Respiratory tract infections (RTIs) pose a significant global health burden, with etiology complicated by frequent pathogen co-infections. Comprehensive data on the epidemiology of co-infections across broad age and demographic spectra remain limited. Methods: This large-scale retrospective study analyzed 9,908 patients with suspected RTIs at a single hospital. Detection of IgM antibodies against eight common pathogens (Influenza A/B, Respiratory syncytial virus, Adenovirus, Mycoplasma pneumoniae, Parainfluenza virus, Coxsackievirus B, Chlamydia pneumoniae) was performed using rapid colloidal gold kits. Positivity rates, co-infection patterns, and their associations with age and gender were analyzed. Results: The overall pathogen detection rate was 33.1%. Influenza A was the most frequently detected pathogen overall, while Influenza B was most common among single infections. Notably, 33.1% of positive cases involved co-infections, with dual infections being most prevalent. The most frequent co-infection pattern was Influenza A with RSV. Age-stratified analysis revealed the highest proportion of co-infections in preschool children (48.3%) and older adults (40.3%), with adults having the lowest rate (28.5%). Significant gender-based differences were observed within specific age groups, such as higher Adenovirus rates in adult males and higher Mycoplasma pneumoniae rates in adult females. Conclusion: This study highlights the high frequency and specific demographic patterns of respiratory pathogen co-infections, underscoring the complexity of RTI etiology. The findings emphasize the need for considering multiple pathogens in clinical diagnosis and suggest that both age and gender may influence infection susceptibility and co-infection risk, informing future surveillance and management strategies.