Respiratory viral infections and early asthma in childhood.

Respiratory viral infections profoundly influence the disease activity of wheezing illnesses and asthma in early childhood. Viral bronchiolitis shares many features with asthma and a subset of children develop recurrent wheezing after their initial illness. Recently mechanisms for virus-induced exacerbations of childhood asthma are beginning to be focused on and defined. Viruses cause systemic immune activation and also produce local inflammation. These factors are likely to affect airway pathogenesis leading to airway narrowing, an increase in mucus production, and eventually bronchospasm, and airway obstruction. These new insights related to the pathogenesis and disease activity are likely to provide new targets for the therapy and prevention of early asthma in childhood.