RecruitingPhase 1Biological interventionInfluenza Human Challenge ModelThis study examines how the immune system responds to the flu virus (H3N2) during and after infection and how the flu virus is transmitted in the environment. The study will used a flu virus called the H3N2 influenza challenge virus which was produced specifically for use in clinical research in controlled conditions. The study will also assess the safety of the H3N2 influenza challenge in healthy subjects. Mild to moderate symptoms are expected based on previous studies with this strain of influenza.