Burden of respiratory syncytial virus among older adults with an acute respiratory infection: a prospective study in six European countries

Respiratory syncytial virus (RSV) primarily affects the respiratory tract, with a high burden among older adults. We aimed to estimate the prevalence and characteristics of RSV-associated respiratory infections in community-dwelling older adults across Europe.

A prospective, observational study was conducted in six European countries over three consecutive RSV seasons (October 2021 until April 2024). Non-RSV vaccinated participants (age ≥60 years) presenting with symptoms of acute respiratory infection (ARI) at general practitioners and outpatient clinics/outpatient hospitals were recruited. RSV and other respiratory viruses were detected using a combined nasal and throat swab. Diary cards and regular phone contacts were used to collect information on onset and resolution of symptoms. The prevalence of RT-PCR confirmed RSV-ARI (cRSV-ARI) was estimated, as well as symptom duration, underlying comorbidities, prevalence of RT-PCR confirmed RSV lower respiratory tract disease (cRSV-LRTD), complications, hospitalizations, and co-infections.

A total of 2573 participants were enrolled (139 with cRSV-ARI). The prevalence of cRSV-ARI varied by season: 3.6% in Season 1, 9.3% in Season 2, and 4.2% in Season 3. The most frequently reported upper respiratory, lower respiratory, and systemic symptoms were nasal congestion/rhinorrhea, cough, and fatigue (cRSV-ARI: 83.1%, 97.8%, and 64.0%; non-cRSV-ARI: 78.0%, 95.0%, and 68.2%). The overall prevalence of cRSV-LRTD was 3.9% in Season 1, 12.5% in Season 2, and 7.3% in Season 3.

This study highlights the substantial burden of RSV among older adults in Europe and reflects the shift in RSV epidemiology due to the COVID-19 pandemic, indicating a return to pre-pandemic seasonality trends.