Participation in this study will last approximately 6 months. Participants will be admitted to an inpatient unit, where they will stay for 10 full days. On their second day in the unit, participants will receive a single dose of the virus, delivered via nose drops. Twice each day while participants are inpatients, they will undergo physical exams and have their vital signs recorded. Nasal washes and blood samples will be collected before participants receive the virus, and then daily nasal washes will be collected until they are discharged from the inpatient unit. Participants will be discharged from the unit on the 9th day after receiving virus if their nasal wash from Day 8 was free of virus. Follow-up visits will occur 28, 120, and 180 days after participants receive the virus. During follow-up visits nasal washes and blood samples will be collected.