Acute bronchitis is frequently a component of an upper respiratory infection (URI) caused by rhinovirus Common Cold The common cold is an acute, usually afebrile, self-limited viral infection causing upper respiratory symptoms, such as rhinorrhea, cough, and sore throat. Diagnosis is clinical. Handwashing... read more , parainfluenza Parainfluenza Virus Infections Parainfluenza viruses include several closely related viruses that cause many respiratory illnesses varying from the common cold to an influenza-like syndrome or pneumonia; croup is the most... read more , influenza A or B virus Influenza Influenza is a viral respiratory infection causing fever, coryza, cough, headache, and malaise. Mortality is possible during seasonal epidemics, particularly among high-risk patients (eg, those... read more , respiratory syncytial virus Respiratory Syncytial Virus (RSV) and Human Metapneumovirus Infections Respiratory syncytial virus and human metapneumovirus infections cause seasonal lower respiratory tract disease, particularly in infants and young children. Disease may be asymptomatic, mild... read more , coronavirus Coronaviruses and Acute Respiratory Syndromes (MERS and SARS) Coronaviruses are enveloped RNA viruses that cause respiratory illnesses of varying severity from the common cold to fatal pneumonia. Numerous coronaviruses, first discovered in domestic poultry... read more , or human metapneumovirus Respiratory Syncytial Virus (RSV) and Human Metapneumovirus Infections Respiratory syncytial virus and human metapneumovirus infections cause seasonal lower respiratory tract disease, particularly in infants and young children. Disease may be asymptomatic, mild... read more . Bacteria, such as Mycoplasma pneumoniae Mycoplasmas Mycoplasmas are ubiquitous bacteria that differ from other prokaryotes in that they lack a cell wall. Mycoplasma pneumoniae is a common cause of pneumonia, particularly community-acquired pneumonia... read more , Bordetella pertussis Pertussis Pertussis is a highly communicable disease occurring mostly in children and adolescents and caused by the gram-negative bacterium Bordetella pertussis. Symptoms are initially those of nonspecific... read more , and Chlamydia pneumoniae C. pneumoniae Three species of Chlamydia cause human disease, including sexually transmitted infections and respiratory infections. All are susceptible to macrolides (eg, azithromycin), tetracyclines (eg... read more , 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 Asthma Asthma is a disease of diffuse airway inflammation caused by a variety of triggering stimuli resulting in partially or completely reversible bronchoconstriction. Symptoms and signs include dyspnea... read more , chronic obstructive pulmonary disease [COPD] Chronic Obstructive Pulmonary Disease (COPD) Chronic obstructive pulmonary disease (COPD) is airflow limitation caused by an inflammatory response to inhaled toxins, often cigarette smoke. Alpha-1 antitrypsin deficiency and various occupational... read more 
, bronchiectasis Bronchiectasis Bronchiectasis is dilation and destruction of larger bronchi caused by chronic infection and inflammation. Common causes are cystic fibrosis, immune defects, and recurrent infections, though... read more 
, cystic fibrosis Cystic Fibrosis Cystic fibrosis is an inherited disease of the exocrine glands affecting primarily the gastrointestinal and respiratory systems. It leads to chronic lung disease, exocrine pancreatic insufficiency... read more 
) 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 and Signs 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 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 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 Community-Acquired Pneumonia Community-acquired pneumonia is defined as pneumonia that is acquired outside the hospital. The most commonly identified pathogens are Streptococcus pneumoniae, Haemophilus influenzae, atypical... read more 
(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 Diagnosis Pertussis is a highly communicable disease occurring mostly in children and adolescents and caused by the gram-negative bacterium Bordetella pertussis. Symptoms are initially those of nonspecific... read more 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 Gastroesophageal Reflux Disease (GERD) Incompetence of the lower esophageal sphincter allows reflux of gastric contents into the esophagus, causing burning pain. Prolonged reflux may lead to esophagitis, stricture, and rarely metaplasia... read more 
, can usually be made on the basis of the clinical presentation. Differentiation of cough-variant asthma Asthma Asthma is a disease of diffuse airway inflammation caused by a variety of triggering stimuli resulting in partially or completely reversible bronchoconstriction. Symptoms and signs include dyspnea... read more 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 of routine use of other symptomatic treatments, such as antitussives, mucolytics, and bronchodilators, is weak. Antitussives Treatment Cough is an explosive expiratory maneuver that is reflexively or deliberately intended to clear the airways. It is one of the most common symptoms prompting physician visits. (See also Cough... read more 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 Antibiotic Resistance Antibacterial drugs are derived from bacteria or molds or are synthesized de novo. Technically, “antibiotic” refers only to antimicrobials derived from bacteria or molds but is often (including... read more argue against widespread antibiotic use. Oral antibiotics are typically not used except in patients with pertussis Pertussis Pertussis is a highly communicable disease occurring mostly in children and adolescents and caused by the gram-negative bacterium Bordetella pertussis. Symptoms are initially those of nonspecific... read more 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.
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.
