High-risk groups Certain patients are at high risk of complications from influenza: Children < 5 years; children < 2 years are at particularly high risk Adults > 65 years People with chronic medical disorders (eg, cardiopulmonary disease, diabetes mellitus, renal or hepatic insufficiency, hemoglobinopathies, immuodeficiency) Women in the 2nd or 3rd trimester of pregnancy Patients with disorders that impair handling of respiratory secretions (eg, cognitive dysfunction, neuromuscular disorders, stroke, seizure disorders) Patients ≤ 18 years taking aspirin (because Reye syndrome is a risk) Morbidity and mortality in these patients may be due to exacerbation of underlying illness, acute respiratory distress syndrome, primary influenza pneumonia, or secondary bacterial pneumonia.