Background：Respiratory syncytial virus (RSV) is the single most common cause of lower respiratory tract infections in infants and young children. RSV can be classified into two major groups, A and B with subgroups based on their reactivity with monoclonal antibodies. There were no reports on the subgroups of RSV isolates in Korea. The purpose of this study is to identify RSV isolates from patients with lower respiratory tract infections to subgroup level and to examine clinical characteristics of subgroup infections.

Methods：RSV infection was diagnosed by viral culture of nasopharyngeal aspirates in patients with lower respiratory infection. Forty two RSV isolates over four successive outbreaks (94/95, November 1994-January 1995; 95/96, Nov. 95-Jan. 96; 96/97, Nov. 96-Jan. 97; 97/98, Nov. 97-Jan. 98) were subgrouped by indirect immunofluorescence with subgroup-specific monoclonal antibodies. Clinical characteristics of subgroup infections were evaluated by review of medical records.

Results：Twenty eight (67%) isolates were identified as group A and 14 (37%) strains as group B. Group A isolates of the 94/95, 95/96, and 96/97 seasons were subgroup A/4, and those of 97/98 season were subgroup A/2. Group B isolates were all identified as subgroup B/2. There was no statistically significant difference in clinical characteristics according to the subgroup infections.

Conclusions：This study show that RSV subgroup A/4, A/2 and B/2 isolated over recent four successive epidemic seasons in Seoul. There was no significant difference in clinical characteristics or severity according to the subgroup infections. (Korean J Clin Microbiol 1999;2:8~13)