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 followingsigns and/or symptoms consistent with a viral acute respiratory infection (ARI),within 5 days prior to randomization: nasal congestion, nasal discharge, sorethroat, 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 studyparticipation or, in the investigator's judgment, make the participant inappropriatefor the study or interfere with the evaluation of response to the studyintervention.

• Diagnosis of viral respiratory infections other than RSV including influenza andSARS-CoV-2

• Current need for hospitalization or anticipated need for hospitalization for anyreason to provide inpatient/acute care within 24 hours after randomization

• Any clinically significant ECG abnormality in the pre-dose ECG that, perinvestigator judgement, may affect participant safety

• Has hypersensitivity to or other contraindication to any of the components of thestudy interventions, as determined by the investigator.