Characterisation of respiratory syncytial virus activity in children and adults presenting with acute respiratory illness at primary care clinics in Singapore, 2014-2018

Background Respiratory syncytial virus (RSV) is an important respiratory pathogen that affects people of all ages. Objectives We examined the patterns of RSV circulation in 2014-2018, and investigated their age-specific differences in tropical Singapore. Methods Nasopharyngeal and/or throat swabs were taken from outpatient attendees for the national influenza virological surveillance among those who presented with acute respiratory illness in the community. Specimens tested negative for influenza were then tested for RSV and other respiratory pathogens. Results Among 8436 influenza-negative specimens tested during the five-year period, 5.8% (95% confidence interval 5.3%-6.3%) were positive for RSV. The peak of RSV activity occurred around middle of the year. The age-specific proportion of RSV detections showed a reverse J-shaped pattern; RSV positivity was the highest in young children <= 2 years of age (10.9%), followed by those aged 3-5 years (6.4%) and persons aged >= 65 years (5.3%), while the nadir was observed in the age group of 15-24 years (1.2%). RSV type A was predominantly circulating in children <= 5 years of age from 2014 to 2015 and 2017, whereas in 2016, they were more affected by type B. Conclusion Respiratory syncytial virus was more frequently detected among the two age groups that have been recommended for influenza vaccination; persons >= 65 years of age and children 6 months to <5 years of age. Characterisation of RSV activity in the community helps to better inform public health policies for effective prevention and control interventions.