Viral Assessments

After collection, NPAs were frozen at −70 to −80 °C for local storage. The maximum time from NPA collection to storage in freezers was 2 hours. Periodically, NPA was sent to a central laboratory for detection of the following viruses by reverse-transcription polymerase chain reaction (RT-PCR) followed by PCR product hybridization on low-density microarrays, using CLART PneumoVir (Genomica, Madrid, Spain): RSV (A and B), influenza virus (A, A subtype H1N1, and B), parainfluenza (I and III), adenovirus, rhinovirus, metapneumovirus (A and B), bocavirus, and coronavirus (229E). Results were not known immediately by investigators, so patient care was based on clinical presentation, and was thus only available at the time of statistical analysis.