Bronchitis is an infection of the air passages that connect the windpipe to the lungs. It causes swelling and irritation of the airways. With acute bronchitis you usually have a cough that produces phlegm and pain behind the breastbone when you breathe deeply or cough.

Bronchitis often occurs when viruses infect the respiratory tract, such as colds and flu. Bronchitis may also be caused by bacterial infections. It may occur with childhood illnesses such as measles and whooping cough.  Attacks are most frequent during the winter or when the level of air pollution is high.  Infants, young children, older adults, smokers, and people with lung or heart disease are most likely to get acute bronchitis.