Development and Progression of the Common Cold
While the common cold may be caused by over 200 distinct and continually evolving viral pathogens; rhinoviruses, coronaviruses and respiratory syncytial viruses appear to be some of the most common (Turner 2009; Nussenbaum 2010; Worrall 2011; CDC 2012C).
Infection occurs when the cold-causing virus comes into contact with mucous membranes in the nose or eyes. Common cold infections generally result in a non-specific acute inflammatory response that stimulates the release of various inflammatory cytokines and other immune mediators. In fact, many of the symptoms associated with the common cold are a result of inflammation caused by this immune response, rather than by the virus itself (Turner 2009; Turner 2011; Hayden 2011; Pappas 2009). For example, the release of a proinflammatory peptide called bradykinin is a major contributor to sore throat symptoms (Turner 2009; Proud 1988). Stuffy nose symptoms result from increased pooling of blood in nasal blood vessels and increased nasal secretions. Likewise, runny nose occurs due to enhanced permeability of nasal blood vessels, which allows serum to leak into the nasal mucosa (Turner 2011).
Although infection with a virus known to cause the common cold generates an adaptive immune response that helps protect against repeated infection by the same or very similar virus, the sheer volume of distinct viruses that can cause the common cold makes developing immunity against the common cold itself very challenging (Hayden 2011; Turner 2009, Turner 2011). However, infection by a cold virus can decrease the risk and severity of re-infection with the same virus (Turner 2009).