An acute exacerbation of chronic obstructive pulmonary disease or acute exacerbations of chronic bronchitis (AECB), is a sudden worsening of chronic obstructive pulmonary disease (COPD) symptoms including shortness of breath, quantity and color of phlegm that typically lasts for several days.
It may be triggered by an infection with bacteria or viruses or by environmental pollutants. [Source: Wikipedia 
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