section_path: Pathophysiology
section_name: Pathophysiology
paragraph_text: Pathophysiology
  
  The symptoms of the common cold are believed to be primarily related to the immune response to the virus. The mechanism of this immune response is virus-specific. For example, the rhinovirus is typically acquired by direct contact; it binds to humans via ICAM-1 receptors and the CDHR3 receptor through unknown mechanisms to trigger the release of inflammatory mediators. These inflammatory mediators then produce the symptoms. It does not generally cause damage to the nasal epithelium. The respiratory syncytial virus (RSV), on the other hand, is contracted by direct contact and airborne droplets. It then replicates in the nose and throat before spreading to the lower respiratory tract. RSV does cause epithelium damage. Human parainfluenza virus typically results in inflammation of the nose, throat, and bronchi. In young children, when it affects the trachea, it may produce the symptoms of croup, due to the small size of their airways.