Bronchitis is a condition wherein air passages into the lungs are inflamed. It can either be chronic or acute. Acute bronchitis is caused by viral infection which starts in the sinuses or nose spreading to the air passages. It can be only considered a chronic bronchitis if the cough progress on the sputum for a minimum of three months within a year. Nevertheless, chronic bronchitis most often affects smokers. In some cases, COPD (chronic obstructive pulmonary disease) is diagnosed.