Bronchitis is an infection of the bronchi, which are large airways that lead to the lungs. Bronchitis can be caused by either a bacterial or viral infection, although viral infections make up over 90% of bronchitis cases. Since the majority of cases are viral infections, antibiotics will have no effect on symptoms. Thankfully, bronchitis is not usually serious and clears up on its own in a few weeks. Even if antibiotics aren’t needed, there are some ways you can treat the symptoms of bronchitis.