Bronchitis is an inflammation of the main air passages (bronchi) to the lungs. Coughing often brings up yellow or greenish mucus. There are two main types of bronchitis: acute and chronic. Acute bronchitis , often caused by the same viruses that cause colds, usually starts as a sore throat, runny nose or sinus infection, then spreads to your airways. It can cause a lingering dry cough, but it usually goes away on its own. In chronic bronchitis , a type of chronic obstructive pulmonary disease (COPD) , the inflamed bronchi produce a lot of mucus, leading to cough and difficulty getting air in and out of the lungs.