Role of viral coinfections in asthma development

BACKGROUND Viral respiratory infections, especially acute bronchiolitis, play a key role in the development of asthma in childhood. However, most studies have focused on respiratory syncytial virus or rhinovirus infections and none of them have compared the long-term evolution of single versus double or multiple viral infections. OBJECTIVE Our aim was to compare the frequency of asthma development at 6-8 years in children with previous admission for bronchiolitis associated with single versus double or multiple viral infection. PATIENTS & METHODS A cross-sectional study was performed in 244 children currently aged 6-8 years, previously admitted due to bronchiolitis between September 2008 and December 2011. A structured clinical interview and the ISAAC questionnaire for asthma symptoms for 6-7-year-old children, were answered by parents by telephone. Specimens of nasopharyngeal aspirate for virological study (polymerase chain reaction) and clinical data were prospectively taken during admission for bronchiolitis. RESULTS Median current age at follow-up was 7.3 years (IQR: 6.7-8.1). The rate of recurrent wheezing was 82.7% in the coinfection group and 69.7% in the single-infection group, p = 0.06. The number of wheezing-related admissions was twice as high in coinfections than in single infections, p = 0.004. Regarding the ISAAC questionnaire, 30.8% of coinfections versus 15% of single infections, p = 0.01, presented "wheezing in the last 12 months", data that strongly correlate with current prevalence of asthma. "Dry cough at night" was also reported more frequently in coinfections than in single infections, p = 0.02. The strongest independent risk factors for asthma at 6-8 years of age were: age > 9 months at admission for bronchiolitis (OR: 3.484; CI95%: 1.459-8.317, p:0.005), allergic rhinitis (OR: 5.910; 95%CI: 2.622-13.318, p<0.001), and viral coinfection-bronchiolitis (OR: 3.374; CI95%: 1.542-7.386, p:0.01). CONCLUSIONS Asthma at 6-8 years is more frequent and severe in those children previously hospitalized with viral coinfection-bronchiolitis compared with those with single infection. Allergic rhinitis and older age at admission seem also to be strong independent risk factors for asthma development in children previously hospitalised because of bronchiolitis.