Bronchitis occurs when the bronchioles are inflamed and make too much mucus. There are two basic types of bronchitis Chronic bronchitis is defined as cough productive of sputum that persists for three months out of the year for at least two consecutive years. The cough and inflammation may be caused by initial respiratory infection or illness, exposure to tobacco smoke, or other irritating substances in the air. Acute or short-term bronchitis is more common and usually is caused by a viral infection. Episodes of acute bronchitis can be related to and made worse by smoking. Acute bronchitis could last for 10 to 14 days, possibly causing symptoms for three weeks.