Acute bronchitis is the sudden inflammation of the tracheobronchial tree, which comprises the trachea, or windpipe (tube that leads from the throat to the lungs) and the bronchi (bronchial tubes, air passages of the lungs). It is typically associated with a viral upper respiratory tract infection (URI), such as the common cold, and is usually mild. In patients with chronic lung or heart disease, acute bronchitis is more severe, and can become chronic (chronic obstructive pulmonary disease [COPD]) and progress to pneumonia.
Infection causes the mucous membrane of the bronchial tubes to become inflamed and produce thick, sticky mucus. The overproduction of mucus reduces the normal defensive function (called clearing function) of the cilia, the small hairlike structures of the bronchial tubes responsible for moving secretions and debris out of the lungs. Inflammation and accumulated mucus narrow the airways, restrict respiration, and promote bacterial infection.
The viruses that cause this condition are often transmitted when they are expelled through coughing, sneezing, and talking. They can also be transmitted through contact with infected drinking glasses and eating utensils.
Types of Bronchitis
Acute infectious bronchitis commonly accompanies or follows a URI; it develops over a couple of days, produces symptoms for 3 to 7 days, and resolves to a cough before normal respiratory function is recovered. Acute irritative bronchitis is triggered by allergies and chemical and other types of environmental irritants.
Incidence & Prevalence of Bronchitis
Acute bronchitis is one of the most common conditions treated by primary-care physicians. Incidence is highest in the winter. It frequently affects people who suffer from allergies, other respiratory illnesses, chronic sinusitis, chronic tonsillitis, infected adenoids, and smokers.
Causes & Risk Factors for Bronchitis
The most common viruses associated with bronchitis are influenzavirus types A and B, which cause influenza; and rhinovirus, parainfluenza, and coronavirus, which cause the common cold. Viral infection may create an environment in which bacterial infection also can develop. Bacterial infection with Mycoplasma pneumoniae, Clamydia pneumoniae, and Bordetella pertussis (whooping cough), particulary in young adults, can lead to acute bronchitis.
Bronchitis risk factors include the following:
- Air pollutants
- Chronic sinusitis
- Lack of pertussis immunization
- Malnutrition (particularly in children)
- Exposure to chemicals, fumes, and dust
- Smoke inhalation