Q. I've had several bouts of acute bronchitis in the past year. What causes it, and is it contagious?
A. Acute bronchitis is an inflammation of the breathing tubes in the lungs. It comes on suddenly and lasts for at least five days, often longer.
Most often acute bronchitis is caused by an infection, usually with a virus. Influenza (the "flu" virus) and the viruses that cause the common cold are the most frequent culprits. Occasionally, acute bronchitis is caused by a bacterial infection, particularly with Chlamydia pneumoniae and Mycoplasma pneumoniae.
Acute bronchitis is different from pneumonia — an infection not of the breathing tubes but of the tiny air sacs in the lung (called alveoli) where our bodies absorb oxygen. Pneumonia is a more serious condition (it can even be life-threatening) and usually requires treatment with antibiotics.
Acute bronchitis causes a cough and sometimes pain in the chest. The cough can be "dry" or "wet." A wet cough expels material from the lungs: mucus and sometimes white blood cells from the inflammation. Often, acute bronchitis follows a common cold that has produced sneezing and runny nose for several days before the cough starts. A fever is unusual in acute bronchitis, and if you have a fever along with your cough, that increases the possibility that you have pneumonia.
When you seek medical care because of a bad cough, the main thing your doctor focuses on is whether your cough is caused by acute bronchitis or by something else. If the doctor thinks it is acute bronchitis, you will probably not have any tests. If the doctor suspects a condition other than acute bronchitis (particularly pneumonia), he or she may order tests: a chest x-ray, an examination of the sputum you are coughing up, and blood tests to detect bacterial infection or other conditions that cause cough. For acute bronchitis, you probably will not get antibiotic or antiviral drugs; they are unlikely to be effective, and they're not necessary, since acute bronchitis resolves on its own. You may get medicine to suppress your cough.
Acute bronchitis often is contagious. For that reason, whenever you start coughing, it is important to always cough into a handkerchief, to avoid coughing into peoples' faces, and to keep washing your hands. The viruses and bacteria that can cause acute bronchitis can be spread by touch (like a handshake) as well as by contaminating the air that others breathe in.
If you have had several bouts of what was diagnosed as acute bronchitis, your doctor may wonder if you have an underlying condition that can cause a long-term or recurring cough. These conditions range from mild to serious.
— by Anthony L. Komaroff, M.D.
Editor in Chief, Harvard Health Letter
