RT Journal Article SR Electronic T1 Examining the interseasonal resurgence of respiratory syncytial virus in Western Australia JF Archives of Disease in Childhood JO Arch Dis Child FD BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health SP e1 OP e7 DO 10.1136/archdischild-2021-322507 VO 107 IS 3 A1 Foley, David Anthony A1 Phuong, Linny Kimly A1 Peplinski, Joseph A1 Lim, Selina Mei A1 Lee, Wei Hao A1 Farhat, Asifa A1 Minney-Smith, Cara A A1 Martin, Andrew C A1 Mace, Ariel O A1 Sikazwe, Chisha T A1 Le, Huong A1 Levy, Avram A1 Hoeppner, Tobias A1 Borland, Meredith L A1 Hazelton, Briony A1 Moore, Hannah C A1 Blyth, Christopher A1 Yeoh, Daniel K A1 Bowen, Asha C YR 2022 UL http://adc.bmj.com/content/107/3/e1.2.abstract AB Background Following a relative absence in winter 2020, a large resurgence of respiratory syncytial virus (RSV) detections occurred during the 2020/2021 summer in Western Australia. This seasonal shift was linked to SARS-CoV-2 public health measures. We examine the epidemiology and RSV testing of respiratory-coded admissions, and compare clinical phenotype of RSV-positive admissions between 2019 and 2020.Method At a single tertiary paediatric centre, International Classification of Diseases, 10th edition Australian Modification-coded respiratory admissions longer than 12 hours were combined with laboratory data from 1 January 2019 to 31 December 2020. Data were grouped into bronchiolitis, other acute lower respiratory infection (OALRI) and wheeze, to assess RSV testing practices. For RSV-positive admissions, demographics and clinical features were compared between 2019 and 2020.Results RSV-positive admissions peaked in early summer 2020, following an absent winter season. Testing was higher in 2020: bronchiolitis, 94.8% vs 89.2% (p=0.01); OALRI, 88.6% vs 82.6% (p=0.02); and wheeze, 62.8% vs 25.5% (p<0.001). The 2020 peak month, December, contributed almost 75% of RSV-positive admissions, 2.5 times the 2019 peak. The median age in 2020 was twice that observed in 2019 (16.4 vs 8.1 months, p<0.001). The proportion of RSV-positive OALRI admissions was greater in 2020 (32.6% vs 24.9%, p=0.01). There were no clinically meaningful differences in length of stay or disease severity.Interpretation The 2020 RSV season was in summer, with a larger than expected peak. There was an increase in RSV-positive non-bronchiolitis admissions, consistent with infection in older RSV-naïve children. This resurgence raises concern for regions experiencing longer and more stringent SARS-CoV-2 public health measures.Data may be obtained from a third party and are not publicly available. De-identified data may be obtained upon request through the Perth Children's Hospital ethic and governance system.