Upper respiratory infection: An infection of the upper part of the respiratory system which is above the lungs. An upper respiratory infection can be due to any number of viral or bacterial infections. These infections may affect the throat (pharyngitis), nasopharynx (nasopharyngitis), sinuses (sinusitis), larynx (laryngitis), trachea (tracheitis) or bronchi (bronchitis).
Upper respiratory infection is commonly abbreviated URI.
