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 in the current pandemic. 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.
Symptoms are a nonproductive or mildly productive cough accompanied or preceded by URI symptoms, usually by > 5 days. Subjective dyspnea results from chest pain or tightness with breathing, not from hypoxia.
Signs are often absent but may include scattered rhonchi and wheezing. Sputum may be clear, purulent, or occasionally contain streaks of blood. 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 is based on clinical presentation. Microbiologic testing is usually unnecessary. However, patients with signs or symptoms of COVID-19 in the current pandemic 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, as 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). Viral panel testing is not usually recommended because results do not affect treatment.
Cough resolves within 2 weeks in 75% of patients. Patients with persistent cough should undergo a chest x-ray. The decision to evaluate for noninfectious causes, 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.
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 of routine use of other symptomatic treatments, such as antitussives, mucolytics, and bronchodilators, is weak. Antitussives should 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.
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. Oral antibiotics are typically not used except in patients with pertussis or 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.