Aim-The aim of the study was to describe the frequency of viral pathogens and relative frequency of co-infections in nasal specimens obtained from young children with bronchiolitis receiving care at a children's hospital.Methods-We conducted a study of nasal wash specimens using real-time PCR and fluorescentantibody assay results from children less than two with an ICD-9-CM code for bronchiolitis. All specimens were collected for clinical care at Children's Hospital in Seattle, WA, USA, during the respiratory season from October 2003 to April 2004.Results-Viruses were detected in 168 (93%) of the 180 children with bronchiolitis. A single virus was identified in 127 (71%) children and multiple viruses in 41 (23%). Respiratory syncytial virus (RSV) was the most common virus detected (77%), followed by adenovirus (15%), human metapneumovirus (11%), coronavirus (8%), parainfluenza (6%) and influenza (1%). Of the 139 samples with RSV detected, 34 (24%) were co-infected with another viral pathogen.Conclusion-Molecular diagnostic techniques identified a high frequency of viruses and viral co-infections among children evaluated for bronchiolitis. Further study of the role of viral pathogens other than RSV and co-infections with RSV in children with bronchiolitis appears warranted.

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UL97 drug-resistant mutations occur in pediatric transplant recipients with CMV viremia and can cause serious disease. Screening for mutations conferring resistance to CMV antivirals should be considered for patients with persistent viremia during therapy and the sequences of UL97 mutations evaluated.