A Study to Learn About the Study Medicine Sisunatovir in Adults With Respiratory Syncytial Virus (RSV) Infection

Inclusion Criteria: Participants aged 18 years or older at screening. Diagnosis of RSV infection collected within 5 days prior to randomization. New onset or worsening (if present chronically) of at least one of the following signs and/or symptoms consistent with a viral acute respiratory infection (ARI), within 5 days prior to randomization: nasal congestion, nasal discharge, sore throat, cough, sputum production, shortness of breath, or wheezing. Has at least 1 of the following characteristics or underlying medical conditions: a) 65 years of age or older b) Chronic lung disease, c) Heart failure, d) Immunosuppressive disease/condition or immune-weakening medications Exclusion Criteria: Any medical or psychiatric condition that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study or interfere with the evaluation of response to the study intervention. Diagnosis of viral respiratory infections other than RSV including influenza and SARS-CoV-2 Current need for hospitalization or anticipated need for hospitalization for any reason to provide inpatient/acute care within 24 hours after randomization Known history or has risk factors for QT prolongation or Torsades de Pointes or congenital deafness, family history of long QT syndrome or unexplained sudden death, or a standard 12-lead ECG with QTcF ≥450 ms Has hypersensitivity to or other contraindication to any of the components of the study interventions, as determined by the investigator.