Acute bronchitis is inflammation of the windpipe (trachea) and the airways that branch off the trachea (bronchi) caused by infection.
Bronchitis can be either acute or chronic.
Symptoms of acute bronchitis usually last days to a few weeks. However, bronchitis that lasts up to 90 days is still usually classified as acute bronchitis. Bronchitis that lasts longer, sometimes for months or years, is usually classified as chronic bronchitis. When chronic bronchitis occurs together with a decrease in the rate of airflow from the lungs when the person breathes out (expiratory airflow), it is considered a defining characteristic of chronic obstructive pulmonary disease (see Chronic Obstructive Pulmonary Disease (COPD)). This chapter discusses acute bronchitis only.
Exposure to irritants, such as smoke, smog, dust particles, and fumes (from irritants such as strong acids, ammonia, some organic solvents, chlorine, hydrogen sulfide, sulfur dioxide, and bromine), can also inflame the windpipe and bronchi, causing symptoms similar to those of acute bronchitis.
Acute bronchitis is caused by infection due to
Bronchitis occurs most often during the winter and is most often caused by viruses. Viral bronchitis may be caused by a number of common viruses, including the influenza virus. Even after a viral infection has cleared up, the irritation it causes can continue to cause symptoms for weeks.
Bronchitis may also be caused by bacteria. Bacterial bronchitis occasionally follows a viral upper respiratory infection. Mycoplasma pneumoniae, Chlamydia pneumoniae, and Bordetella pertussis infection (which causes whooping cough) are among the bacteria that cause acute bronchitis. Bacterial causes of acute bronchitis are more likely when many people are affected (an outbreak).
If people who have chronic lung disorders such as COPD, bronchiectasis, or cystic fibrosis develop inflammation of their trachea and bronchi, the inflammation is considered a flare (exacerbation) of the underlying disorder rather than acute bronchitis.
Infectious bronchitis generally begins with the symptoms of a common cold: runny nose, sore throat, fatigue, and chilliness. Back and muscle aches together with a slight fever (100° to 101° F, or 37.5° to 38° Celsius [C]) may be present, particularly if the infection is due to influenza. The onset of cough (usually dry at first) signals the beginning of acute bronchitis. With viral bronchitis, small amounts of white mucus are often coughed up. This mucus often changes from white to green or yellow. The color change does not mean there is a bacterial infection. Color change means only that cells associated with inflammation have moved into the airway and are coloring the sputum.
When bronchitis is severe, fever may be slightly higher at 101° to 102° F (38° to 39° C) and may last for 3 to 5 days, but higher fevers are unusual unless bronchitis is caused by influenza. Cough is the last symptom to subside and often takes 2 to 3 weeks or even longer to do so. Viruses can damage the epithelial cells lining the bronchi, and the body needs time to repair the damage.
Airway hyperreactivity, which is a short-term narrowing of the airways with impairment or limitation of the amount of air flowing into and out of the lungs, is common in acute bronchitis. The impairment of airflow may be triggered by common exposures, such as inhaling mild irritants (for example, perfume, strong odors, or exhaust fumes) or cold air. If the impairment of airflow is severe, the person may be short of breath. Wheezing, especially after coughing, is common.
Older people may have unusual symptoms, such as confusion or rapid breathing, rather than fever and cough.
Serious complications, such as acute respiratory failure (see Respiratory Failure) or pneumonia (see Overview of Pneumonia), usually occur only in people who are older, or who have problems with immune defenses.
Doctors usually make a diagnosis of bronchitis based on the symptoms. Fevers that are high or prolonged or both could indicate the presence of pneumonia (see Overview of Pneumonia). Doctors may hear wheezing during the physical examination. A chest x-ray is sometimes done to exclude pneumonia, for example, when doctors hear crackles or congestion in the lungs or when the person is short of breath.
A sample taken from the throat or nose can be used to detect influenza viruses or Bordetella pertussis if infections with those organisms seem likely. Sputum is generally only examined if doctors find evidence of pneumonia on a chest x-ray or during the examination. If a cough persists for more than 2 months, a chest x-ray is done to exclude an underlying lung disease, such as lung cancer.
Adults may take aspirin, acetaminophen, or ibuprofen to reduce fever and general feelings of illness, but children should take only acetaminophen or ibuprofen, not aspirin, because children taking aspirin are at higher risk for Reye syndrome (see Reye Syndrome). People with acute bronchitis, especially those who have a fever, should drink plenty of fluid.
Antibiotics are not used to treat bronchitis except for people whose infection is caused by bacteria (for example, during an outbreak). When an antibiotic is used, a drug such as azithromycin or clarithromycin is most often given. Antibiotics do not help people with viral bronchitis. Treatment with an antiviral drug for influenza such as oseltamivir or zanamivir may help speed recovery from influenza (whether or not it causes acute bronchitis) if given within 48 hours of the onset of symptoms.
In children, very mild symptoms of limited airflow can be helped with cool-mist humidifiers or steam vaporizers. In more severely affected children and adults who are wheezing, inhaled bronchodilators, which widen the bronchi, can be used to open the airways and reduce wheezing.
Cough medicines (see Cough suppressants) can be used to suppress a dry, disturbing cough, particularly when it interferes with sleep. However, the degree of effectiveness of these drugs is not clear. Also, a cough that produces a lot of sputum usually should not be suppressed. Expectorants may help to thin secretions and make them easier to cough up, but whether this measure is helpful is not clear.
Last full review/revision September 2014 by Sanjay Sethi, MD