The study will take place in a quarantine facility. Some volunteers (Donors) will be infected with the influenza virus via droplets into the nose. Other volunteers (Recipients) will then be exposed to them by occupying the same room (in the day time) and taking part in certain activities e.g. playing card games. Some of the Recipients will wear face shields and clean their hands regularly during the times they are with the Donors. The wearing of face shields together with good hand hygiene should reduce the spread of infection through large respiratory droplets and contact with contaminated surfaces but will not prevent infection that occurs through aerosols in the air. Use of symptom diaries and diagnostic tests for influenza will allow the presence of subsequent illness to be identified. Volunteers will be required to participate in the quarantine facility for up to approximately 13 days (typically 9 for Donors and 13 days for Recipients), plus study screening clinics and followup.