As long as you have active symptoms, avoid other people. The viruses that cause acute bronchitis are highly contagious, just like the common cold or influenza. You can return to school or work after your symptoms have gone away. If you have a slight cough, make sure you cover your mouth and nose.
Acute bronchitis caused by a bacterial infection is less contagious, but can still be passed along to vulnerable populations like infants and the elderly. Once you begin taking antibiotics, you’ll stop being contagious after 48 hours.