OBJECTIVES: Respiratory Syncytial Virus (RSV) is a common respiratory virus that usually causes mild, cold-like symptoms. Most people recover in a week or two, but the virus can be much more serious, especially for infants, young children, and older adults. RSV has been a notifiable disease in Ireland since January 2012. RSV activity in Ireland is monitored and reported by the Health Protection Surveillance Centre (HPSC). The objective of this study is to understand RSV incidence over time, by age group and by seasonality in Ireland.

METHODS: A full dataset of RSV incidence in Ireland for the years 2012–2023 was obtained from the HPSC. An RSV season was defined as the weeks when RSV detections are ≥1.2% of total RSV-positive specimens. The RSV season runs from week 40 in one year to week 20 the following year (October to May) while the non-RSV season runs from week 21 (June) in one year to week 39 (September) the following year. Descriptive analysis of the data, by age group and seasonality was then conducted to understand the trends and patterns of RSV incidence since 2012.

RESULTS: RSV notifications have increased by 226% since 2012/13 in Ireland. At least 89% of cases occur during the RSV season. Children aged 0–4 years account for at least 73% of RSV cases every year. The number of older adults with RSV has increased almost six-fold between the 2012/13 and 2022/23 seasons and represented 22% of all notifications in 2022/23.

CONCLUSIONS: The number of RSV cases, especially in infants and older adults, has increased significantly over the past decade in Ireland. This may be due to an increase of RSV infection or because more hospitals are testing for RSV, in recent years when they were not previously.