Is bronchitis bacterial or viral?

Usually viral: Acute bronchitis is usually caused by viruses, typically the same viruses that cause colds and influenza. The most common cause of chronic bronchitis is smoking cigarettes. Air pollution and dust or toxic gases in the environment or workplace also can contribute to the condition. Antibiotics as a whole are overprescribed in bronchitis, though sometimes it is warranted.

Can be both: Bronchitis can be either acute or chronic. Chronic bronchitis is often caused by chronic irritants like tobacco smoke. Acute bronchitis is most often caused by a viral infection but about 10% of the time it can be caused by a bacterial infection.