Viral bronchiolitis refers to a bronchiolitis secondary to viral aetiology.
Viral infection of airways resulting in inflammation and peribronchial oedema. Can then result in small airways occlusion which is the basis of hyperinflation and subsegmental atelectasis. Children more susceptible due to smaller airways.
Common causative agents include
- respiratory syncytial virus (RSV)-60-70%
- human metapneumovirus (hMPV)-5-15%
- adenovirus types 3,7,21
- parainfluenza virus
May show hyperinflation with increased (commonly bilateral symmetrical) peribronchial thickening and lack or focal lung consolidative change. Can have segmental/subsegmental/band atelectatic changes. Small lobular air trapping. An increased AP diameter may be seen.