Multiple Co-Infections and Risk of Severe Outcomes in Children with Respiratory Syncytial Virus Infection

Objective : To describe the clinical characteristics of co-infections in children with respiratory syncytial virus (RSV) infection and to assess their association with disease severity. Methods: This retrospective study analyzed the medical records of 5,586 children hospitalized with RSV infection at Tianjin Children’s Hospital from January 2018 to January 2023. Patients were categorized into five groups according to co-infection status: RSV alone, RSV with viral co-infection, RSV with bacterial co-infection, RSV with Mycoplasma pneumoniae co-infection, and RSV with multiple co-infections. Demographic data, clinical manifestations, and disease severity were compared across groups. Results Among the enrolled patients, 3,835 had RSV alone, 476 had viral co-infections, 715 had bacterial co-infections, 312 had M. pneumoniae co-infections, and 248 had multiple co-infections. Children with multiple co-infections were significantly older (median, 3 years vs 0.5 years; P <0.001), had longer fever duration and hospital stays, and exhibited higher rates of severe pneumonia than those with single infections (all P <0.05). Viral co-infections were more frequently associated with wheezing and chest retractions, whereas bacterial and M. pneumoniae co-infections were characterized by high fever and cough. Conclusions : Co-infections in RSV-infected children are associated with distinct clinical phenotypes and poorer outcomes. Multiple co-infections substantially increase the risk of severe disease and prolonged illness. Recognition of specific co-infection patterns may facilitate early identification of high-risk children and support tailored management strategies.