Causes of chronic obstructive pulmonary disease
| Causal mechanism | Common | Less common |
| Bacteria | Haemophilus influenzae | Pseudomonas |
| Streptococcus pneumoniaie | ||
| Moraxella catarrhalis | ||
| Virus | Rhinovirus | Influenza A and B |
| Respiratory syncytial virus | Parainfluenza virus | |
| Coronavirus | ||
| Adenovirus | ||
| Atypical organisms | Mycoplasma pneumoniae | |
| Chlamydia pneumoniae | ||
| Noninfective | Air pollution (particulates, ozone) | Pulmonary embolus |
| Cold temperatures | Congestive cardiac failure |