Background:Acute lower respiratory tract infections are common causes of hospitalization in children and viruses are major causative agents. The causative viruses are known to be variable by age, region, or year. We investigated the recent 5-year epidemics of respiratory viruses for pediatric patients in two university hospitals in Korea.

Material and Methods:From July 1996 through June 2001, viral agents were detected for the 2,317 pediatric patients who were hospitalized with acute respiratory tract infection in Hanyang University Hospital and Hanyang University Guri Hospital. We obtained nasopharyngeal aspirates on the day of admission and detected the viruses by indirect immunofluorescent staining method (Respiratory panel I viral Screening & Identification Kit, Light Diagnostics, Chemicon, Temecula, CA, USA).

Results:The causative viral agents were detected in 737(31.76%) patients. They were respiratory syncytial virus of 53.6%, influenza A virus 38.6%, adenovirus 5.5%, influenza B virus 1.9%, and parainfluenzavirus 0.4%. The epidemics of RSV were found during winter, but the epidemics of influenza A were found more frequently in spring, which had tendency of following the epidemic of RSV. Adenovirus was detected sporadically throughout year. RSV was found more frequently in patient with bronchiolitis and pneumonia and also found more frequently in patient less than 6 month of age. Influenza A and adenovirus were in patients of pneumonia and in more frequently in patient one to two year of age.

Conclusion:Viruses were the leading causative agents of acute lower respiratory tract infections in pediatric patients. RSV was the most important causative agent. Influenza A virus was the second frequent viral agent and detection rate was higher than other reports. The detection rate of parainfluenza virus was lower than other reports from Korea or from abroad. (Korean J Clin Microbiol 2002;5:(2)77-83)