The clinical burden of respiratory syncytial virus (RSV) bronchiolitis among infants in the United Kingdom (UK)

Abstract

Background and Aim: Studies of the epidemiology of respiratory syncytial virus (RSV) bronchiolitis to date have been small; focused only on the hospital setting and selective groups of high-risk infants such as those born preterm; lacked long-term follow-up and few have been based on data from the United Kingdom (UK). Hence, the existing evidence base was likely to underestimate the scale and impact of RSV on health in UK infants. The aim of this thesis was to provide better estimates of the wider clinical burden of RSV bronchiolitis among infants presenting across primary and secondary care settings in the UK. Methods: The clinical spectrum of bronchiolitis illness across different healthcare settings was examined using routine data from electronic health records to develop longitudinal, population-based cohorts with follow-up from birth through early childhood. Databases examined in this thesis included Hospital Episodes Statistics (HES), the General Practice Research Database (GPRD) and the National Neonatal Research Database (NNRD). Results: The estimated bronchiolitis admission rate in NHS hospitals in England was 24.2 admissions per 1000 infants aged less than 1 year (95% CI 23.7 to 24.8) with a median length of stay of 1 day (IQR 0 to 3 days) at a median age of 120 days (IQR 61 to 209 days). 15% of infants admitted with bronchiolitis were born preterm (47.3 per 1000 infants) and 24% had at least one known clinical risk factor for severe RSV infection. Cystic fibrosis, cerebral palsy and Down‟s syndrome also increase an infant‟s risk of bronchiolitis admission. The bronchiolitis consultation rate in UK general practice was 58.1 per 1000 infants (95% CI 56.5 to 59.8) at a mean age of 5.5 months (SD=3.2). Using a broader bronchiolitis case definition the estimated consultation rate was 206.7 per 1000 infants (95% CI 204.0 to 209.6). 36% of bronchiolitis consultations resulted in a prescription, of which 28% were for antibiotics and 27% for beta agonists, despite no evidence to support their use. Bronchiolitis in infancy is a predictor of subsequent hospital admissions and general practice consultations for asthma and wheezing in early childhood. Conclusions: The clinical burden of RSV bronchiolitis across healthcare settings in the UK is greater than previously estimated. Between 4% and 21% of infants have a bronchiolitis GP consultation in their first year. 2.4% of the national birth cohort are admitted to hospital with bronchiolitis in the first year of life, most of whom are born at term with no known clinical risk factors for severe RSV infection. This thesis has identified new groups of infants who may be at increased risk of severe RSV disease including those with cystic fibrosis, cerebral palsy and Down‟s syndrome. These findings highlight the need to prioritise development of new approaches for the prevention and treatment of RSV infection and have important implications for clinical training and management of bronchiolitis across healthcare settings.