It is a breathing disorder in which there is inflammation of the breathing tubes (bronchi) causing increased mucous production and swelling of bronchial walls.
A person may have a brief attack of acute bronchitis with fever, cough and spitting from exposure to cold. But a person is said to have chronic bronchitis only when this coughing and spitting continues over a long period and recurs (comes back) over several years.
Hence, Chronic Bronchitis is defined as coughing up sputum for at least 3 months of the year for at least 2 consecutive years (i.e. 2 years in a row) or for 6 months during 1 year.