Features of an Aseasonal 2021 Rsv Epidemic in the Uk and Ireland: Analysis of the First 10,000 Patients

ABSTRACT

Aims Respiratory syncytial virus (RSV) causes annual winter epidemics that usually peak in December in the UK and Ireland. Infants are disproportionately affected, with infection leading to lower respiratory tract disease, most commonly bronchiolitis, that often result in emergency department visits and hospitalisations. Non-pharmaceutical interventions (NPIs) introduced globally to limit the spread of SARS-CoV-2 led to disruption of the typical RSV seasonality. Studies examining the aseasonal resurgence of RSV have been limited by sample size, and lack of information on secondary care episodes and clinical features. The BronchStart study is a prospective multicentre cohort study with the objective to monitor RSV disease in children under two years of age attending emergency departments (EDs) across the UK and Ireland and examine the impact on timing, age and severity of clinical presentations as NPI restrictions are reduced throughout the UK and Ireland in 2021. Methods Paediatric emergency departments (PED) within PERUKI (Paediatric Emergency Research in the UK and Ireland) submit data on all children under 2 years of age who visit a PED with symptoms of an acute lower respiratory tract infection (diagnosed as bronchiolitis, lower respiratory tract infection, or first episode of acute wheeze), to a secure online Research Electronic Data Capture (REDCap) database. Followup information is submitted 7 days later. Here we present initial data for 10,347 infants and children from 44 study sites for the period 1st June to 5th December 2021. Results At the time of submission the aseasonal 2021 RSV epidemic in the UK has now come to an end, with infections having peaked in August (figure 1A). Comparing the age distribution of hospitalised infants <12 months to previous years at two large paediatric centres currently participating in the BronchStart Study (Leicester Children's Hospital and Bristol Royal Hospital for Children), we observed a similar age distribution (figure 1B). This suggests reduced community exposure to RSV during the 15 months preceding the start of the season did not result in a clinically significant lack of protective maternal antibody transfer to those <3 months of age, or that the NPIs introduced were not strong enough to prevent low level transmission. Disease severe enough to require intensive care was 2.5% in our cohort (for those aged 6 weeks to one year), comparable to 4.2% reported in previous studies. We also observed a substantial number of PED visits and admissions for RSV positive 12-23 month old children in BronchStart 362 out of 1,468 (24.7%) admissions were in this age group. Conclusion We found that the 2021 summer lower respiratory tract infection peak in the UK and Ireland, although temporally disrupted and with an attenuated disease burden, predominantly affected younger age groups as in previous years The overall lower burden of disease in 2021 suggests incomplete infection by RSV of its usual susceptible population, probably due to the effect of ongoing non-pharmaceutical interventions over the study time period, and raises the strong possibility of a further wave of infection in the coming months.