Viral respiratory tract infection and exacerbations of asthma in adult patients.

The role of viral respiratory tract infections in acute exacerbations of asthma was studied prospectively in 31 patients with atopic asthma aged 15-56 years. Patients recorded symptom scores for asthma and peak expiratory flow rate daily for 11 months. In addition, they reported for detailed clinical, functional, and virological study every four weeks and as soon as possible after the onset of worsening asthma or symptoms suggesting a respiratory tract infection. Thirty viral identifications were made, of which 18 (60%) were associated with an exacerbation of asthma. Viral respiratory tract infection was identified in 18 (10%) of the 178 exacerbations of asthma, and in 10 (36%) of the 28 severe exacerbations. The frequency of viral identifications in 16 non-asthmatic, control subjects during the same period was similar. It is concluded that viral respiratory tract infections may cause or be associated with exacerbations of asthma in adults, and that they are an important factor in severe exacerbations.