Distribution of RSV subtypes by participant age.

ObjectiveThere is conflicting evidence whether subtypes of Respiratory syncytial virus have different seasonality or are differentially associated with clinical severity. We aimed to explore the associations between disease severity and RSV subtypes RSV-A and RSV-B and to describe the circulation of RSV subtypes pattern by season and age.MethodsActive prospective hospital surveillance for RSV-A and RSV-B in children ResultsBoth RSV-A and B were found to co-circulate throughout all three study seasons, and no clear seasonal pattern was identified. Likewise, we found no association between sex or measures of severity with RSV-A or RSV-B. There was significantly more RSV-A than RSV-B among children with comorbidities.ConclusionsNo association was found between disease severity or sex and RSV subtypes RSV-A and RSV-B in hospitalized young children in Norway.