While serious complications of influenza may include encephalitis, Guillain–Barré syndrome, Reye’s syndrome, myocarditis, renal failure, and myositis, the most common complications in all patients, healthy or not, involve the pulmonary system. Influenza may directly cause a viral pneumonia and it also predisposes to the development of secondary bacterial pneumonias. Patients who present with pneumonia in the setting of influenza infection should be treated with both anti-virals and anti-bacterials. While chemoprophylaxis has a role in certain situations, immunization is recognized as the most important means to reduce the morbidity and mortality due to influenza infection.