ACE2 and bronchiolitis: Similar to SARS-CoV, SARS-CoV-2 uses angiotensin-converting enzyme 2 for host cell entry [33], and this protein is more abundant in pulmonary alveoli and small airways than in large airways, as indicated in a study using single-cell analysis data [34, 35] Mycoplasma pneumoniae, Haemophilus influenzae, influenza virus, and rhinovirus can target small airways and trigger progressive bronchiolitis [36, 37].