Upper Respiratory Tract Infection - Cause

Cause

Over 200 different viruses have been isolated in patients with URIs. The most common virus is called the rhinovirus. Other viruses include the coronavirus, parainfluenza virus, adenovirus, enterovirus, and respiratory syncytial virus.

Up to 15% of acute pharyngitis cases may be caused by bacteria, most commonly Streptococcus pyogenes a Group A streptococcus in Streptococcal pharyngitis ("Strep Throat").

Influenza (the flu) is a more severe systemic illness which typically involves the upper respiratory tract. Influenza is a relatively uncommon cause of influenza-like illness.