Bronchitis - Uncomplicated Acute Disease Background

Introduction

Uncomplicated acute bronchitis is a self-limiting acute lower respiratory tract infection (LRTI) characterized by the sudden onset of cough with or without sputum production, in an otherwise healthy individual. It may be preceded by an upper respiratory tract infection (URTI) (eg common cold).

Epidemiology

Acute bronchitis is one of the most common clinical conditions encountered by physicians. In the United States, roughly 5% of individuals are reported to suffer from acute bronchitis annually. In this region, the highest incidence rates are noted during the winter months and in those younger than 5 years of age. Meanwhile, studies in the United Kingdom showed that the incidence rate of acute bronchitis is at 54 per 1,000 persons with a range of 36 per 1,000 in young men to 225 per 1,000 in those older than 85 years of age. In Asia, the age-standardized incidence rate (ASIR) of LRTI is noted to be most severe in South Asia. Additionally, in a country like Vietnam where acute respiratory tract infections are still the leading cause of mortality and morbidity in the young, acute bronchitis is among one of the most common diagnoses, accounting for as much as 18% of cases. 

Pathophysiology

Pathogenesis of acute uncomplicated bronchitis involves an inflammatory response to infections of the bronchial epithelium of the large airways of the lungs. It begins with mucosal injury, epithelial cell damage, and the release of proinflammatory mediators. This leads to transient airflow obstruction and bronchial hyper-responsiveness. Purulence can result from either bacterial or viral infection.

Etiology

The etiology of acute bronchitis is most commonly viral, accounting for 90% of cases of bronchial inflammation in otherwise healthy adults presenting with acute bronchitis. Influenza A and B, parainfluenza 3, and respiratory syncytial virus (RSV) produce primarily lower respiratory tract disease. While coronavirus, adenovirus, and rhinoviruses more commonly cause upper respiratory tract symptoms. Non-viral causes include Mycoplasma pneumoniae, Chlamydia pneumoniae, and Bordetella pertussis are the most common bacteria associated with acute bronchitis which account for 5–10% of cases. Among these, B. pertussis is most likely to cause a prolonged cough. Environmental cough triggers such as dust, dander, and toxic fume inhalation should be noted.