Objective To investigate the effects of virus coinfection on the severity of respiratory syncytial virus(RSV)bronchiolitis through the clinical analysis of 286 cases.Methods Various virus antibody were measured by using ELISA in 286 cases of RSV bronchiolitis.The frequency of respiratory virus coinfection on the severity of RSV bronchiolitis was observed.Results RSV bronchiolitis complicated with virus coinfection ratio reached 29.37%,especially with the double infection.Compared to patients with RSV infection,the severe cases increased sig-nificantly in patients with virus coinfection(χ2 =128.7,P<0.01).Conclusion Other respiratory viruses coinfection are not uncommon in infants with RSV bronchiolitis and may increase the severity of RSV bronchiolitis.