Bronchitis is inflammation and irritation of the airways (bronchial tubes) of the lungs. The tubes swell and result in symptoms such as a persistent cough that often produces mucus (sputum), fever, mild wheezing, trouble breathing and chest pain.
Bronchitis is usually caused by infection from a virus (less commonly with bacteria or a fungus) like those that cause colds. Antibiotics usually do not help and they may be harmful.
It can also develop after exposure to chemicals or air pollution, including tobacco smoke.