Influenza in People With Normal and Weakened Immune Systems

This study will evaluate how the immune system responds to influenza infection and compare how the infection differs in patients with a weakened immune system versus those with a healthy immune system. Patients at the NIH Clinical Center who are older than 2 years of age and who are diagnosed with influenza A or B may be eligible for this study. Patients with healthy immune systems and weakened immune systems are included. Participants answer questions about how they are feeling and have a physical examination to evaluate their symptoms. Blood and nasal fluid are collected on the first day and then every other day for a total of 8 days. Nasal fluid is collected by either inserting a small tube in the nose and washing the nose with salt water and collecting the fluid obtained, or by rubbing the inside of the nose with a swab. Physical examinations are repeated on the days that blood and nasal fluid are collected.