Influenza:

Influenza is a viral infection of the respiratory tract that causes coughing, breathing difficulty, fever, headache, muscle aches and weakness. The virus is spread from person to person by inhaling infected droplets from the air.
- Reviewed last on: 3/6/2009
- Linda Vorvick, MD, Family Physician, Seattle Site Coordinator, Lecturer, Pathophysiology, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine; and David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.