Acute bronchitis is usually caused by a virus. It is more common during the winter months and often develops after an upper respiratory illness such as influenza (flu) or a cold caused by a virus such as coronavirus, adenovirus, or a rhinovirus. Respiratory syncytial virus (RSV) may be a cause, especially in adults older than 65. About 10% of the time, acute bronchitis is caused by bacteria.¹

Acute bronchitis can also be caused by exposure to smoke, chemicals, or air pollution, all of which can irritate the bronchial tubes. It can also develop from accidentally inhaling (aspirating) food or vomit.

See an illustration of acute bronchitis.

How acute bronchitis is spread

Acute bronchitis is spread when an infected person coughs, sneezes, or talks and liquid droplets containing virus particles or bacteria that may trigger the condition are released into the air and onto objects. Then you may:

• Breathe air that contains the virus particles or bacteria.
• Touch an object that has been touched by an infected person and then touch your eyes, nose, or mouth without washing your hands.