OCCURRENCE OF GROUP-A AND GROUP-B OF RESPIRATORY SYNCYTIAL VIRUS OVER 15 YEARS - ASSOCIATED EPIDEMIOLOGIC AND CLINICAL CHARACTERISTICS IN HOSPITALIZED AND AMBULATORY CHILDREN

Over 15 years respiratory syncytial virus (RSV) isolates from 1209 hospitalized and ambulatory children were examined for strain group and in a subset for subgroup to determine the associated epidemiologic and clinical characteristics. Three patterns of yearly outbreaks existed: (1) strong predominance of group A strains (9 years with 83%–100% A strains), (2) relatively equal proportions of group A and B strains (4 years), and (3) strong predominance of group B strains (78%–85%) in 2 years, separated by a decade. The first pattern of highly dominant A strains occurred in cycles of 1 or 2 consecutive years with a single intervening year in which B strains were ≥40% of the isolates. Subgroups Al and A2 predominated, while B2, 3, and 4 occurred almost equally. A greater clinical severity for Group A strains was suggested bychildren with group A infections requiring intensive care significantly more often (15.4 vs. 8.3%, P =.(08). Further, strongly dominant A strain years were associated with higher proportions of RSV admissions requiring intensive care (16.6% vs. 5.5%, P <.01). Strains of subgroups A2 and B4 were more frequently found in hospitalized patients and Al in outpatients, and the 2 years with the highest rates of intensive care admissions were those in which subgroup A2 dominated. © 1990, by The University of Chicago.