Here's an article about Acute Bronchitis you may find useful. Bronchitis that begins at a discrete time and ends is called "acute" rather than "chronic."
http://www.findarticles.com/cf_dls/m3225/n6_v57/20482452/p1/article.jhtml
True acute bronchitis (per the article) is caused by an infection, commonly caused by a virus. Also (as explained in the article), there can be other causes as well.
Aloha,
Starion
Bronchitis (acute) is swelling and inflammation in the airways of the lungs. Symptoms can include cough with mucus, chest discomfort, fever, and/or extreme tiredness. It is often caused by an infection, which can be due to a bacteria or a virus. This underlying cause of the bronchitis can be contagious. Frequent good hand washing and the use of disposable tissues can decrease the number of acute bronchitis infections. Unless you are having symptoms now you are probably not contagious.