[Epidemiological study of respiratory viruses detected in patients under two years old who required admission because of lower respiratory disease].

The etiologic role of recently identified respiratory viruses for lower respiratory tract disease (LRTD) remains unclear in Japan. The purpose of this study was to investigate the prevalence of respiratory viruses in young children with LRTD. We prospectively examined 721 children who were under two years old and admitted to a single medical center in Japan with LRTD between April 2007 and March 2012. Viral nucleotic acids were taken from their nasal swabs. Each sample was examined with (RT-) PCR for respiratory syncytial virus (RSV), enterovirus (EV), human metapuemovirus (hMPV), human bocavirus (HBoV), parainfluenzavirus (PIV), and adenovirus (AdV). We detected at least one virus agent in 466 (65%); 83 patients (12%) were co-infected with different viruses. No virus was detected in 255 patients (35%). RSV (27%) was most common, followed by EV (11%), hMPV (6.9%), HBoV (3.3%), PIV (2.9%), and AdV (2.2%). Seasonal distribution was seen in each virus. Infants under 6 months old were frequently positive for RSV or EV. In 20 patients (2.8%) who required mechanical ventilation because of respiratory failure, 18 patients were positive for RSV nospace between "and/or" EV.