The role of viral infections in the natural history of asthma

Viral infections have been related to the inception of recurrent wheezing i llnesses and asthma in infants and are probably the most frequent cause of exacerbations of established disease in older children and adults, The well -recognized clinical effects of viral infections are mainly caused by virus -induced immune responses. Clinical studies of natural and experimentally i nduced viral infections have led to the identification of mechanisms of inf lammation that could be involved in producing airway obstruction and lower airway symptoms. In addition, host factors that are associated with more vi gorous viral replication or severe clinical illness are beginning to be ide ntified. Advances in molecular virology and our understanding of immune res ponses to viral infections may lead to the development of new strategies fo r the prevention and treatment of virus-induced respiratory disorders.