All pediatric (from case-patients and controls) and adult (case-patients only) NPA specimens were previously analyzed by using a multiplex real-time PCR assay for infl uenza A and B viruses, human respiratory syncytial virus (hRSV), and human metapneumovirus (hMPV) (24, 25) . For symptomatic children, viral cultures and antigen detection assays were performed upon request by the treating physician. Remaining specimens were frozen at -80°C until subsequent HBoV PCR studies.