Upper respiratory tract infections affect the air passages in the nose, ears, and throat.
Structures of the throat include the esophagus, trachea, epiglottis, and tonsils.
The infections can be caused by viruses, bacteria, or other microscopic organisms. In most cases, these infections lead to colds or mild influenza (flu) and are temporary and harmless. In rare cases, flu can be severe, or the infections may turn into pneumonia.
Organisms that cause these upper respiratory tract infections are generally spread by:
- Direct contact (such as hand-to-mouth)
- Coughing or sneezing
Review Date: 01/29/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.