Lay Summary Respiratory syncytial virus (RSV) causes respiratory illnesses, which can lead to serious complications in older adults. We estimated how common infections due to RSV are in adults living in the community or long-term care facilities. For 2 years, we followed approximately 2000 adults 50 years and older in Europe and the United States. Between October 2019 and March 2020, about 2 in 100 adults in this study had RSV infections; of these, fewer than one fifth had complications and there were no hospitalizations or deaths. Other viruses were present for less than one fifth of RSV infections. Between October 2020 and June 2021, during COVID-19 restrictions, we detected RSV infection in one adult, living in a long-term care facility, with no complications. RSV causes respiratory disease among adults 50 years and older and therefore programs to prevent RSV infection are needed in this age group.

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