Which term describes an infection of the small air-tubes in the lungs?

Bronchiolitis refers specifically to the inflammation and infection of the small air passages in the lungs, known as bronchioles. This condition is often seen in young children and infants, commonly caused by viral infections, particularly the respiratory syncytial virus (RSV).

In contrast, bronchiectasis refers to the permanent enlargement of parts of the airways of the lung and is not primarily an infection. Pneumonia is an infection of the lung tissue itself, affecting the alveoli rather than the small air tubes. Asthma is a chronic condition characterized by airway inflammation and constriction, but it is not primarily an infection. Thus, the term that accurately describes the infection of the small air-tubes in the lungs is bronchiolitis.