Acute bronchitis is inflammation of the tracheobronchial tree, commonly following an upper respiratory infection in the absence of chronic lung disorders. The cause is almost always a viral infection. The pathogen is rarely identified. The most common symptom is cough, with or without fever, and possibly sputum production. Diagnosis is based on clinical findings. Treatment is supportive; antibiotics are usually unnecessary. Prognosis is excellent.
(See also Cough in Children.)
Acute bronchitis is frequently a component of an upper respiratory infection (URI) caused by rhinovirus, parainfluenza, influenza A or B virus, respiratory syncytial virus, coronavirus, or human metapneumovirus. Bacteria, such as Mycoplasma pneumoniae, Bordetella pertussis, and Chlamydia pneumoniae, cause less than 5% of cases; these sometimes occur in outbreaks. Acute bronchitis is part of the spectrum of illness that occurs with SARS-CoV-2 infection, and testing for this virus is appropriate. Fever, myalgias, sore throat, gastrointestinal symptoms, and loss of smell and taste are more common with the SARS-CoV-2 virus than others.
Acute inflammation of the tracheobronchial tree in patients with underlying chronic bronchial disorders (eg, asthma, chronic obstructive pulmonary disease [COPD], bronchiectasis, cystic fibrosis) is considered an acute exacerbation of that disorder rather than acute bronchitis. In these patients, the etiology, treatment, and outcome differ from those of acute bronchitis.
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Symptoms and Signs of Acute Bronchitis
Symptoms are a nonproductive or mildly productive cough accompanied or preceded by URI symptoms. Typical symptom duration before presentation is about 5 days or more. Subjective dyspnea results from chest pain caused by musculoskeletal discomfort due to coughing or chest tightness related to bronchospasm, not from hypoxia.
Signs are often absent but may include scattered rhonchi and wheezing. Sputum may be clear or purulent. Sputum characteristics do not correspond with a particular etiology (ie, viral vs bacterial). Mild fever may be present, but high or prolonged fever is unusual and suggests influenza, pneumonia, or COVID-19.
On resolution, cough is the last symptom to subside and often takes 2 to 3 weeks or even longer to do so.
Diagnosis of Acute Bronchitis
Clinical evaluation
Sometimes chest x-ray to exclude other disorders
Diagnosis is based on clinical presentation. Microbiologic testing is usually unnecessary. However, patients with signs or symptoms of COVID-19 should be tested for SARS-CoV-2. Diagnostic testing for influenza and pertussis should also be considered if there is high clinical suspicion based on exposure and/or clinical features.
Patients who complain of dyspnea should have pulse oximetry to rule out hypoxemia.
Chest x-ray is done if findings suggest serious illness or pneumonia (eg, ill appearance, mental status change, high fever, tachypnea, hypoxemia, crackles, signs of consolidation or pleural effusion). Older patients are the occasional exception, because they may have pneumonia without fever and auscultatory findings, presenting instead with altered mental status and tachypnea.
Sputum Gram stain and culture usually have no role. Nasopharyngeal samples can be tested for influenza and pertussis if these disorders are clinically suspected (eg, for pertussis, persistent and paroxysmal cough after 10 to 14 days of illness, only sometimes with the characteristic whoop and/or retching, exposure to a confirmed case). Testing for Mycoplasma and Chlamydia infection does not affect treatment so is not recommended. Viral panel testing is not usually recommended because results do not affect treatment.
Cough resolves within 2 weeks in 75% of patients; in the other 25%, it may take up to 8 weeks to resolve. Patients with cough that worsens after initial improvement and those with cough that lingers for > 8 weeks should undergo further evaluation, including a chest x-ray. Evaluation for noninfectious causes of chronic cough, including asthma, postnasal drip, and gastroesophageal reflux disease, can usually be made on the basis of the clinical presentation. Differentiation of cough-variant asthma may require pulmonary function testing.
Treatment of Acute Bronchitis
Symptom relief (eg, acetaminophen, hydration, possibly antitussives)
Inhaled beta-agonist for wheezing
Acute bronchitis in otherwise healthy patients is a major cause of antibiotic overuse. Nearly all patients require only symptomatic treatment, such as acetaminophen and hydration. Evidence supporting efficacy ofroutine use of other symptomatic treatments, such as antitussives, mucolytics, and bronchodilators, is weak. Antitussivesshould be considered only if the cough is distressing or interfering with sleep. Patients with wheezing may benefit from an inhaled beta2-agonist (eg, albuterol) for a few days. Broader use of beta2-agonists is not recommended because adverse effects such as tremor, nervousness, and shaking are common. There are no clear indications for mucolytics.
Though some studies have shown modest symptomatic benefits with antibiotic use in acute bronchitis, the low incidence of bacterial causation, self-limiting nature of acute bronchitis, and the risk of adverse effects and antibiotic resistance argue against widespread antibiotic use. Patient education and delayed prescription (ie, to be only filled if no improvement after at least a couple of days) help limit unnecessary antibiotic use. Oral antibiotics are typically not used except in patients with pertussisor during known outbreaks of bacterial infection (mycoplasma, chlamydia). A macrolide such as azithromycin 500 mg orally once, then 250 mg orally once a day for 4 days or clarithromycin 500 mg orally twice a day for 7 days is the preferred choice.
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Key Points
Acute bronchitis is viral in > 95% of cases, often part of an upper respiratory infection.
Diagnose acute bronchitis mainly by clinical evaluation; do chest x-ray and/or other tests only in patients who have manifestations of more serious illness.
Treat most patients only to relieve symptoms.
