Bronchitis is caused by inflammation of the bronchial tubes in the lungs, typically due to viruses (such as those causing colds or the flu), bacteria, or irritation from substances like tobacco smoke, dust, fumes, and air pollution. Acute bronchitis usually results from viral infections and can be contagious through transmission of the underlying viruses or bacteria from person to person by coughing, touching, or close contact. Chronic bronchitis, on the other hand, is mostly caused by long-term exposure to irritants like cigarette smoke, air pollution, or chemical fumes, and is not contagious itself. Risk factors include smoking, exposure to lung irritants, having asthma or allergies, a weakened immune system, and working in environments with chemical fumes or dust.
