Association of viral etiology with disease severity in bronchiolitis.

Acute bronchiolitis is a leading cause of lower respiratory tract infections in young children. While multiple viruses contribute to its pathogenesis, their impact on disease severity remains unclear. In this cross-sectional observational study, children with bronchiolitis were enrolled. Baseline characteristics, bronchiolitis severity score, Respiratory Distress Assessment Instrument score, duration of hospitalization, and respiratory support requirements were recorded. Nasopharyngeal aspirates were analyzed via real-time polymerase chain reaction. Among 52 enrolled children (median age: 3 months), viruses were detected in 33 (63.5%) children. Of these, 6 (11.5%) had co-infection with more than one virus. Human rhinovirus (HRV) was the most common (39.4%), followed by respiratory syncytial virus (RSV) (33.3%), parainfluenza virus (PIFV) (21.2%), enterovirus (EV) (12.1%), influenza virus (6.1%), and both human metapneumovirus (hMPV) and human coronavirus (3.0% each). Co-infections involved HRV-RSV (n=2), HRV-EV (n=2), RSV-PIFV (n=1), and EV-PIFV (n=1). HRV was significantly associated with mild bronchiolitis (p=0.03), while other viruses and co-infections did not impact severity. Children aged 13-24 months had a significantly longer median hospital stay than younger age groups (p=0.04). Notably, despite recent concerns about hMPV in younger children, we found only one case, presenting with mild bronchiolitis and no respiratory support requirement. HRV is linked to milder bronchiolitis, while other viruses and co-infections do not significantly influence severity. These findings highlight regional viral variations and the need for larger studies to guide management.