Clinical significance and pathogenesis of viral respiratory infections.

Viral respiratory tract infections, also known as colds, are the most common infection in humans. The majority of these infections are caused by rhinoviruses. Rhinovirus deposition in the nose or the eye initiates infection. The virus attaches to the host cell intercellular adhesion molecule-1 (ICAM-1) receptors in the back of the throat. Subsequent viral replication triggers the release of inflammatory mediators and activation of neurogenic pathways, which lead to symptoms. Symptoms occur within 10 to 16 hours after virus entry into the nose and peak on days 2 to 3 of infection. Symptom duration is typically 1 week, although 25% of cases last longer. Understanding the chronology of these events is important in the timing of treatment. Because of the rapidity of symptom onset, early treatment is the key to reducing viral replication and illness. Also, early treatment may reduce the risk of transmission.