The role of respiratory viruses in the pathogenesis of pediatric asthma.

The role of respiratory viral infection in the development of asthma remains unclear. A number of factors play crucial roles, including the type of virus, the severity of the disease, the time of the infection, and, most important, the host predisposition. On the other hand, there is little doubt that a strong association exists between viral respiratory infections and induction of wheezing illnesses and asthma exacerbations. The underlying mechanisms, although not fully clarified, are likely to be multifactorial, involving inflammation of the bronchial mucosa, which interacts under certain circumstances with allergic inflammation. In addition, repetitive infections play an important role in perpetuating inflammation and airway hyperresponsiveness, especially in the presence of atopy, leading from childhood asthma to a more persistent asthma phenotype.