EFFECT OF INFLUENZA-A VIRUS-INFECTION ON ACID-INDUCED COUGH RESPONSE IN CHILDREN WITH ASTHMA

Although it is well-known that some types of respiratory viral infecti ons cause airway hyperresponsiveness in humans, the effect of viral in fection on the cough threshold in asthmatics is not known. We, therefo re, evaluated the effects of naturally-acquired influenza A virus infe ction on the cough threshold to inhaled acid in children with asthma. Twelve children with asthma (9 boys and 3 girls, mean+/-SEM age of 10. 8+/-0.6 yrs), who had naturally-acquired influenza A virus infection i n winter (January-February, 1992) during an epidemic of influenza A (H 1N1), were enrolled in this prospective, uncontrolled study. All patie nts underwent acetic acid (AA) inhalation challenge 2, 4 and 6 weeks a fter the influenza infection. The cough threshold values (the lowest c oncentrations of AA eliciting coughs) after 2, 4 and 6 weeks of the il lness were 3.7+/-0.9, 5.3+/-1.0 and 8.1+/-1.4% (mean+/-SEM), respectiv ely. Cough threshold values 4 or 6 weeks after the illness improved si gnificantly over that at 2 weeks (p<0.05 and p<0.01, respectively). In contrast, baseline forced expiratory volume in one second did not cha nge throughout the study. These results indicate that influenza A viru s infection attenuates the cough threshold independently of airway obs truction in children with asthma. The enhanced cough response followin g virus infection is probably mediated by damage to the airways epithe lium. (C)ERS Journals Ltd 1997.