Respiratory syncytial virus infection in lower respiratory tract and asthma attack in hospitalized children in North Hokkaido, Japan.

Respiratory syncytial virus (RSV) infection is severe and life-threatening in some infants. To investigate the epidemiology of RSV infection in hospitalized children in North Hokkaido, Japan, we tried to detect RSV antigen in nasopharyngeal aspirates (NPA) from those children with lower respiratory tract infection (LRTI) and asthma attack. From April 1991 to March 1992, 317 patients were hospitalized in our pediatric ward for the treatment of LRTI and asthma attack. The presence of RSV antigen in NPA taken from 283 patients (89.3%) were examined by enzyme immunoassay. RSV antigen was detected in 88 patients (31.1%). RSV LRTI were noted throughout the year, and the epidemic peak was observed in November and December. There was no significant correlation between the RSV antigen positive rate and mean temperature. RSV played an important role in LTRI in children in North Hokkaido, Japan. RSV LRTI in North Hokkaido was not rare in summer, indicating that RSV was transmitted commonly among children throughout the year.