Mechanisms of respiratory virus-induced asthma exacerbations

---For many years, general opinion has been that respiratory virus infections were the cause of the common cold and were able to produce serious pulmonary complications only in infants, the elderly and immunocompromised subjects. It is now widely recognized that respiratory viral infections are also the most important causes of asthma exacerbations both in children and adults [1]. The health costs of asthma exacerbations are enormous in terms of days lost from work or school, general practitioner consultations, hospital admissions and mortality [2]. Despite optimized therapy for stable asthma with inhaled glucocorticoids and long‐acting β2‐agonists, asthma exacerbations continue to occur suggesting that the pathogenesis of asthma exacerbations and of stable asthma are likely to be different [3]. The cellular and molecular mechanisms underlying these events have been studied and partially elucidated in the last few years but more studies are needed to fully understand the mechanisms of asthma exacerbations so that new more effective therapies can be developed. We will review the relationship between respiratory virus infections and the cellular and molecular mechanisms involved in the activation of the lower airway inflammatory response that occurs during asthma exacerbations.