Viral etiology of acute febrile respiratory illnesses in hospitalized children younger than 24 months.

Background: Respiratory infections are a leading cause of pediatric hospitalizations. This study investigated whether virus-virus or virus-Bordetella co-infections are more frequent or more severe than previously recognized. Methods: This is a 3-year prospective study of children younger than 24 months hospitalized with a febrile respiratory illness. Viral pathogens were detected using multiplex polymerase chain reaction (PCR), enzyme-linked immunoassays, and/or viral cultures from nasopharyngeal samples. Bordetella infections were detected by PCR. Results: A total of 201 patients were enrolled. Respiratory viruses were detected in 187 (93%) patients, with 52 (28%) multipathogen infections. The most common viruses detected were respiratory syncytial virus and rhinovirus/enterovirus. There were no differences in illness severity when comparing patients infected with one pathogen and those with multipathogen infection. Conclusion: Virus co-infection in young children hospitalized with an acute febrile respiratory infection is common but does not appear to be associated with illness severity.