The point prevalence of respiratory syncytial virus in hospital and community-based studies in children from Northern Australia: studies in a 'high-risk' population.

INTRODUCTION:Respiratory syncytial virus (RSV) is the leading viral cause of acute lower respiratory infections globally, accounting for high morbidity and mortality burden among children aged less than 5 years. As candidate RSV vaccine trials in pregnant women and infants are underway a greater understanding of RSV epidemiology is now needed, especially in paediatric populations with high rates of acute and chronic respiratory disease. The objective was to identify RSV prevalence in children living in northern Australia, a region with a high respiratory disease burden. METHODS:Data were sourced from 11 prospective studies (four hospital and seven community-based) of infants and children with acute and chronic respiratory illnesses, as well as otitis media, conducted between 1996 and 2017 inclusive. The data from northern Australian children in these trials were extracted and, where available and consented, their nasopharyngeal swabs (biobanked at -80ºC) were tested by polymerase chain reaction assays for RSV-A and B, 16 other viruses and atypical respiratory bacterial pathogens. RESULTS:Overall, 1127 children were included. Their median age was 1.8 years (interquartile range 0.5-4.9); 58% were male and 90% Indigenous, with 81% from remote communities. After human rhinoviruses (HRV), RSV was the second most prevalent virus (15%, 95% confidence interval (CI) 13-18). RSV prevalence was greatest amongst children aged less than 2 years hospitalised with bronchiolitis (47%, 95%CI 41.4-52.4), with more than two-thirds with RSV aged less than 6 months. In contrast, the prevalence of RSV was only 1-3.5% in other age groups and settings. In one-third of RSV cases, another respiratory virus was also detected. Individual viruses other than RSV and HRV were uncommon (0-9%). CONCLUSION:Combined data from 11 hospital and community-based studies of children aged less than 18 years who lived in communities with a high burden of acute and chronic respiratory illness showed that RSV was second only to HRV as the most prevalent virus detected across all settings. RSV was the most frequently detected virus in infants hospitalised with bronchiolitis, including those aged less than 6 months. In contrast, RSV was uncommonly detected in children in community settings. In northern Australia, effective maternal and infant RSV vaccines could substantially reduce RSV bronchiolitis-related hospitalisations, including admissions of Indigenous infants from remote communities.