Abstract Background Acute bronchiolitis in infancy, commonly caused by respiratory syncytial virus (RSV) or rhinovirus (RV), has been associated with later development of allergic diseases, particularly asthma. However, the relationship between viral etiology and allergic predisposition remains unclear. This study aimed to compare the clinical and allergic characteristics of bronchiolitis according to causative viruses. Methods We retrospectively reviewed medical records of children under 24 months of age hospitalized with acute bronchiolitis between 2013 and 2022, in whom multiplex PCR identified the causative virus. Demographic data, allergic background (family history of allergic diseases, atopic dermatitis, serum IgE, eosinophil count), and clinical outcomes were compared among virus groups, focusing on RSV and RV. Results Among 1,024 episodes, RSV (36.1%) was the most common, followed by RV (11.6%), parainfluenza (6.4%), and metapneumovirus (4.8%).Children with RV bronchiolitis were older (median 10.2 vs. 5.6 months, p 0.001) and more likely to have a family history of allergic disease (38.7% vs. 21.4%, p = 0.004) and atopic dermatitis (26.1% vs. 12.3%, p = 0.008) than those with RSV bronchiolitis. During 12-month follow-up, recurrent wheezing occurred more frequently in the RV group (31.8% vs. 14.7%, p 0.001; adjusted OR 2.12, 95% CI 1.34-3.35). Conversely, RSV infection was associated with younger age, greater hypoxia (oxygen requirement 58.9% vs. 34.5%, p 0.001), and longer hospital stay (median 5.2 vs. 3.8 days, p 0.01). No significant intergroup differences were found in serum total IgE levels (p = 0.41) or peripheral eosinophil counts (p = 0.33). Conclusions The viral etiology of acute bronchiolitis is associated with distinct allergic and clinical profiles. Rhinovirus bronchiolitis tends to occur in older infants with an atopic background and predicts a higher risk of recurrent wheezing, whereas RSV bronchiolitis primarily affects younger infants with more severe acute illness. Recognition of these patterns may help identify infants at increased risk for later allergic airway disease. This abstract is funded by: None
Kim et al. (2026) studied this question.