Respiratory syncytial virus subtype circulation and associated disease severity at an Australian paediatric referral hospital, 2014-2018.

<bold>Aim: </bold>Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections in children and the development of vaccines to protect at-risk groups is a global priority. The aim of this study was to describe RSV subtype circulation patterns and associated disease severity to inform on potential impact of an RSV-specific prevention strategy.<bold>Methods: </bold>Single-centre retrospective observational study of children aged <16 years with laboratory-confirmed RSV infection from 2014 to 2018 inclusive. We described the features and frequency of all RSV subtype detections. We selected a random sample of RSV-A and RSV-B cases from each year (n = 200), described demographic and clinical features of these cases, and compared indicators of disease severity between subtypes.<bold>Results: </bold>We identified 3591 RSV detections over a 5-year period and found consistent co-circulation of subtypes with alternating predominance. Demographic and clinical characteristics were similar between children presenting with RSV-A and RSV-B infections. There was no difference in indicators of severity between the subtypes except for paediatric intensive care unit length of stay which was longer in the RSV-B group (3 vs. 5 days, P = 0.006). Respiratory co-infections were more frequent in the RSV-B group (41.8% vs. 27.4%, P = 0.035). When these were excluded there was no longer a detectable difference in paediatric intensive care unit length of stay.<bold>Conclusions: </bold>We found co-circulation of RSV subtypes and no convincing evidence of a difference in disease severity between subtypes. RSV-specific interventions will need to be equally effective against both RSV-A and RSV-B to have the greatest impact on reducing severe RSV disease in this population. [ABSTRACT FROM AUTHOR]