Acute bronchitis generally follows a viral respiratory infection. The viral infection produces bronchial inflammation, which sets the stage for bronchitis and secondary bacterial infection.

Chronic bronchitis is a long-term condition of excessive bronchial mucus with a productive cough. Chronic bronchitis is also known as chronic obstructive pulmonary disease.

Cigarette smoking (active and passive exposure) is the chief cause of this disease. Factors that make it worse include air pollution, infection, familial factors like genetic history and allergies.

The severity of the disease often relates to the amount and duration of smoking. Chronic bronchitis, emphysema, and asthma as a group are the fourth-leading cause of death in the United States. Two to three out of 100 people have chronic bronchitis.