Viruses attack the lining of the bronchial tree, causing damage. As the body fights back against these viruses, more swelling occurs and more mucus is made. Even though the body kills off the viruses, it takes time for the body to repair the damage caused by the infection. During this time, one may continue to cough and wheeze. Anything that causes further damage to the bronchial tree, such as cigarette smoking, will lengthen the time it takes for one to get better.
Acute bronchitis is spread from person to person by coughing.
The viruses that cause the infection are sprayed into the air or onto people's hands when they cough. One can catch acute bronchitis if one breathes in the viruses or touch hands coated with these viruses or use the handkerchiefs or towels of the infected person. One is more likely to get acute bronchitis if the bronchial tree is already damaged. People who smoke are more likely to get acute bronchitis and to have it longer. Pollution in the atmosphere can also lead to worsening of the existing condition.