Two cases of asthmatic exacerbation caused by parainfluenza virus 3 infection

: Although viral respiratory tract infections are considered to be the most frequent causes of asthmatic exacerbation, respiratory viruses can rarely be detected in the adult population. We describe 2 cases, in a 43-yr-old man with severe atopic asthma and in a 69-yr-old man with moderate non-atopic asthma. After the onset of nasal discharge, sore throat and fever, the asthma had become exacerbated in both cases during the summer of 2002. In both cases, parainfluenza virus (PIV) 3 viral RNA could be detected from oral gargling by RT-PCR, and the serum viral antibody titer against PIV 3 increased significantly. These cases were therefore diagnosed as undergoing asthmatic exacerbation caused by PIV 3 infection and were successfully treated with systemic steroids. During summer, 2002, in our outpatient clinic, PIV 3 infection was demonstrated in approximately half of the asthmatic exacerbations associated with upper respiratory symptoms, including the present cases. Collectively, PIV 3 seems to represent an important viral cause of asthma exacerbation in summer.