Etiology

The majority of common colds are caused by rhinoviruses (up to 50%), of which there are many.[1][8] Other known pathogens include coronavirus (10% to 15%), influenza (5% to 15%), parainfluenza (5%), respiratory syncytial virus (5%), and metapneumovirus.[1] Often, no infecting organisms are identified. Reinfection can occur after re-exposure to the same viral subtype, but the illness is typically milder and of shorter duration. There is an association with adenoviruses and enteroviruses and the common cold. Pharyngitis is commonly due to adenoviruses, which can also cause lower respiratory infections. Common respiratory tract bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis) may be associated with the common cold.[9] However, this has no implications in terms of antibiotic treatment for the typical common cold.

Pathophysiology

An influx of polymorphonuclear leukocytes (PMNs) in the nasal submucosa occurs within a few days after viral inoculation and correlates with symptoms.[10][11] There is no evidence that purulent discharge is related to bacterial infection or responds to antibiotics.[1]

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