Bronchitis is most contagious as long as a cough persists. 

More Info: Bronchitis is caused by a swelling in the bronchial tubes that leads to mucus collecting in the lungs. Anyone who has a fever or is still coughing could spread the illness to another person because bronchitis is highly contagious.

How Bronchitis Spreads

Bronchitis travels in a viral form, much like a common cold. Therefore, it can be spread through contact or through germs that travel through the air. You can contract bronchitis by spending time with a person who is ill, especially if that person is running a fever. Bronchitis can be spread through coughs, sneezing, or contact with an object that has been handled by someone who is suffering from the illness. The best defense against spreading bronchitis is to wash your hands thoroughly and cover all coughs with a tissue. Bronchitis is the least contagious during the earliest stages of the illness before the coughing and sneezing starts.

While Running a Fever

The most contagious stage of bronchitis is when the sufferer has a fever. This is the time when the virus is most active and can be spread through simply sharing a confined space with someone who has been infected. If you have bronchitis, you should stay at home until your fever breaks. Confining yourself to bed during this highly contagious stage of bronchitis will also allow you to rest and recover more quickly. It is best to wait at least 24 hours after your fever breaks before you return to regular activities.

As Long as Coughing Persists

Unfortunately, bronchitis is still contagious as long as you are coughing or sneezing. Once the most severe symptoms of bronchitis have passed, you may feel perfectly fine except for a lingering cough. Make sure that you take precautions to protect other people from your coughs and sneezes so that you do not spread the illness among your friends and colleagues. Wash your hands often and do not share items such as drinking cups or silverware until your cough has completely gone away. The virus can continue to live on contaminated surfaces for several hours, so it is important to clean your hands often.