Objective: To investigate the prevalence of 14 viruses in infants with bronchiolitis and to study demographic and clinical differences in those with respiratory syncytial virus (RSV), human bocavirus (hBoV), and rhinovirus (RV) infection.
Patients, design and examinations: 182 infants less than 12 months old hospitalized for bronchiolitis were enrolled. Infants underwent nasal washing for the detection of RSV, influenza virus A and B, human coronavirus OC43, 229E, NL-63, HUK1, adenovirus, RV, parainfluenza 1-3, human metapneumovirus and hBoV. Demographic, clinical and laboratory data were obtained from parents with a questionnaire and from patient’s medical files.
Main outcome measurements: Age, breast-feeding history, family smoking habits, family history of asthma and atopy, blood eosinophil count, chest radiological findings, clinical severity score and number of days of hospitalization.
Results: A virus was detected in 57.2% of the 182 infants. The most frequently detected viruses were RSV (41.2%), hBoV (12.2%) and RV (8.8%). Infants with dual infections (RSV and hBoV) had a higher clinical severity score and more days of hospitalization than infants with RSV, RV and hBoV bronchiolitis (mean+SD, 4.7 + 2.4 vs 4.3+2.4 vs 3.0+2.0 vs 2.9+1.7, p<0.05; and 6 + 3.2 vs 5.3+2.4 vs 4.0+1.6 vs 3.9+1.1 days; p<0.05) . Infants with RV infection had higher blood eosinophil counts than infants with bronchiolitis from RSVand hBoV (307+436 vs 138+168 vs 89+19 (n/mm3); p<0.05).
Conclusions: Although the major pathogen responsible for bronchiolitis remains RSV, the infection can be caused also by RV and hBoV. Demographic characteristics and clinical severity of the disease may depend on the number of viruses or on the specific virus detected.