Viral infections in exacerbations of asthma and chronic obstructive pulmonary disease.

Respiratory viral infections are recognized as the most frequent cause of asthma and chronic obstructive pulmonary disease (COPD) exacerbations with rhinovirus (i.e. the virus of the common cold) being the most frequent identified virus. The recent development of human experimental models of rhinovirus-induced asthma and COPD exacerbations represent innovative tools with the potential to increase our understanding in this field. Moreover this models will provide the opportunity to test, in a carefully controlled setting, novel pharmacological compounds. In this review we will provide an overview of the role of viral infections in asthma and COPD exacerbations and in particular we will summarize the inflammatory and immunological mechanisms that can pave the way to exacerbation following respiratory viral infection in these patients.