Respiratory infections and asthma.

Airway responsiveness is increased during respiratory virus infections, both in subjects with asthma and without underlying pulmonary disease. Furthermore, the airway hyperresponsiveness is altered for a prolonged period of time, weeks or months after the viral illness has subsided. This article reviews the possible mechanisms of virus-associated airway hyperresponsiveness, including the complex interplay of IgE-dependent reactions, changes in autonomic nervous system function and inflammation, epithelial damage, effects of viruses on the cellular immune response, and enhanced late-phase response.