THE ROLE OF RESPIRATORY VIRUSES IN ACUTE AND CHRONIC ASTHMA

Respiratory tract infections caused by viruses, 24, 70 chlamydia, 18, 19, 43, 55, 116 and mycoplasma(61) have been implicated in the pathogenesis of asthma. Viruses have been demonstrated to be associated with asthma epidemiologically in at least two ways (Fig. 1). First, during infancy, certain viruses have been implicated as potentially being responsible for the inception of the asthmatic phenotype. Second, in patients, particularly children, with established asthma, viral upper respiratory tract infections play a significant role in producing acute exacerbations of airway obstruction that may result in frequent outpatient visits or hospitalizations. 24, 55, 56, 57 This article reviews these two areas by focusing first on mechanisms by which virus infections may lead to the development of asthma in infants and children and, second, on mechanisms by which virus infections may produce acute asthmatic symptoms in patients who already have established disease.