Acute bronchitis is a self-limited lower respiratory tract infection that is more common in young children and the elderly, especially during cold seasons.^[1][2][3] Viruses, especially influenza, are the most common causative agents.^[4][2][5] Symptoms include: cough, sputum production and wheezing as well as constitutional symptoms. It must be differentiated from pneumonia, asthma, and GERD.^[3] Reassurance and symptomatic medications are mainstays of acute bronchitis.^[2][6] Acute bronchitis may be prevented by hand hygiene, vaccination, and environmental control.^[3][7] Smoking cessation plays a great role in reducing the course of the disease.^[8]

Acute bronchitis was first described by Charles Badham in 1808 in England.^[9] In 1821, Dr. Rene Laennec, known as the “father of chest medicine,” described bronchitis in details.^[10]

The causative agent is transmitted through the large and medium size airway tracts and inoculates the tracheobranchial epithelium. This leads to inflammation, thickening, and increased mucus production in the airways.^[1] Epithelial-cell desquamation and denuding of the airway to the level of the basement membrane in association with the presence of a lymphocytic cellular infiltrate have been demonstrated on microscopic examination.^[1]

Common causes of acute bronchitis include viruses, bacteria and environmental factors. Among them, influenza is common.^[4][2][5]

When bronchitis is prolonged, consider:

• Mycoplasma pneumonia
• Chlamydia pneumoniae
• Bordetella pertussis

Also consider pneumonia and atypical pneumonia.

Acute bronchitis must be differentiated from other diseases that may cause cough, dyspnea, and wheezing^[3] including, pneumonia,^[11] Asthma^[12] Chronic bronchitis,^[13] and GERD^[14][15]

Acute bronchitis is the ninth most common illness among outpatient visits in the U.S. It’s prevalence depends on season of the year, vaccination status and outbreaks during that particular year. It is common among young children and the elderly.^[16][2][17]

The main determining risk factors for acute bronchitis are age, season of the year and the immunization status^[1][2][3].

If left untreated, acute bronchitis usually resolves within 2 weeks but may last up to 2 months.^[1][18] Prognosis is generally excellent and majority of patients recover after 5-10 days.^[2] Recurrent episodes of acute bronchitis in subsequent years occur in 20% of patients.^[3]

History and symptoms^[2][6]

• Bronchial irritation symptoms including: cough, hoarseness, and phlegm production

• Constitutional symptoms including: Chest pain, Fever, malaise, and Myalgia

Physical examination

• Acute bronchitis presents with signs of prolonged expiration, wheezing, fever and abnormal breath sounds.^[3][2]

Laboratory Tests

• Diagnostic tests are rarely needed to confirm the diagnosis of acute bronchitis. In very specific conditions, serologic tests, viral cultures or sputum analyses may be applied. Generally, inflammatory markers, such as CRP, rise during the course of acute bronchitis. Procalcitonin is helpful to differentiate bacterial from other causes.

Chest x-ray

• Normal lung view is the typical finding on chest x-ray.^[3][19]

Medical therapy

• Reassurance and symptomatic therapy are the mainstay of treatment. NSAIDs, albuterol and antitussives may help alleviate symptoms.
• The most important treatment aspect is to NOT routinely prescribe antibiotics.^{[20][21][7][2][22]}
• Azithromycin can treat:
  • Mycoplasma pneumonia
  • Chlamydia pneumoniae
  • Bordetella pertussis

Primary prevention

• The major preventive measures for acute bronchitis include: hands hygiene, environmental control, wearing physical barriers, and vaccination for preventable pathogens, such as influenza and pertussis^[3][7].

Secondary prevention

• Smoking cessation or reduction is helpful in reducing the severity of acute bronchitis symptoms.^[23]

Acute bronchitis was first described by Charles Badham in 1808. Dr. Rene Laennec described this disease in greater detail in 1821.

• Acute bronchitis was first described by Charles Badham in 1808 in England. He classified acute bronchitis into three forms by his definition (Br.acuta, asthenica and chronica).^[1]
• In 1821, Dr. Rene Laennec, known as the “father of chest medicine,” in part to his invention of the stethoscope, described bronchitis in terms of emphysema and chronic bronchitis.^[2]

The pathologic process starts with the inoculation of tracheobranchial epithelium with invading organism, which leads to inflammation, thickening and increased mucus production.

• The causative agent is transmitted through the large and medium size airway tracts.^[1]
• Following transmission, the agent inoculates the tracheobronchial epithelium.
• This process leads to inflammation, thickening, and increased mucus production in the airways compared to normal bronchi as shown below:

• 
  Normal Bronchi
• 
  Inflamed Bronchi

• On microscopic analysis, epithelial-cell desquamation and denuding of the airway to the level of the basement membrane, in association with the presence of a lymphocytic cellular infiltrate, have been demonstrated.^[2]

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Common causes of acute bronchitis include viruses, bacteria and environmental factors. Among these causes, influenza virus is the most common cause, especially during the winter.^[1]

• Acute Bronchitis may be caused by either viral, bacterial or environmental factors.
• Influenza virus is the most common overall cause.^[1][2][3]

• Adenovirus
• Bordetella pertussis
• Hemophilus influenzae
• Influenza virus
• Moraxella catarrhalis
• Mycoplasma pneumoniae
• Rhinovirus
• Streptococcus pneumoniae

Acute bronchitis must be differentiated from other causes of cough and wheezing including: acute exacerbation of chronic bronchitis, asthma and pneumonia.

The acute bronchitis must be differentiated from other diseases that may cause cough, dyspnea and wheezing.^[1]

Acute bronchitis is the ninth most common illness among outpatient visits in the U.S. It’s prevalence depends on season of the year, vaccination status and outbreaks during that particular year. It is common among young children and the elderly.

Acute bronchitis, as a lower respiratory tract infection, is one of the most common illnesses seen among outpatient visits especially in young children.^[1][2][3]

• Acute bronchitis affects approximately 5% of adults in the U.S. annually and it becomes more common during cold seasons. Generally, it depends on the season of the year, vaccination status and presence of an epidemic.
• Acute bronchitis affects around 44 in 1000 adults (age over 16 years) per year in the UK, with around 82% of episodes occurring in autumn or winter.^[4]

• Acute bronchitis is most common among young children.

• Acute bronchitis affects men and women equally.

• There is no racial predilection for acute bronchitis.

Age, season of the year, and the immunization statusare the main determining risk factors for acquiring acute bronchitis.

• Very young and very old persons are at greatest risk.^[1]

• Acute bronchitis is more common during cold seasons than spring and summer.^[2][3]

• Patients who have not been vaccinated for influenza have increased risk.^[1]

Screening is not recommended for acute bronchitis.

Acute bronchitis is a self limited respiratory disease with an excellent prognosis which resolves within two weeks in majority of patients.

If left untreated, acute bronchitis usually resolves within 2 weeks although it may last up to 2 months.^[1][2]

When bronchitis is prolonged, consider:

• Mycoplasma pneumonia
• Chlamydia pneumoniae
• Bordetella pertussis. 13% to 32% of adolescents and adults with a cough lasting six days or more may have B. pertussis.^[3][4]

Also consider pneumonia and atypical pneumonia.

The most common complication of acute bronchitis is persistent cough that my last for 6 weeks.^[5] Rarely, in patients with immunosuppression or other debilitating disease, pneumonia occurs as a complication.^[6]

Prognosis is generally excellent and most of patients recover after 5-10 days.^[5] Recurrent episodes of acute bronchitis in subsequent years occur in 20% of patients.^[6]

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