Acute Bronchitis

Acute bronchitis is inflammation of the tracheobronchial tree, predominantly viral in aetiology. It is characterised principally by cough, which may persist for several weeks even after other symptoms have resolved.

It is one of the commonest reasons for inappropriate antibiotic prescribing in respiratory illness, because bacterial infection is frequently, though generally mistakenly, presumed on the basis of cough alone.

Aetiology

The respiratory viruses responsible for the common cold and other upper respiratory tract infections account for the majority of cases (rhinovirus, coronavirus, influenza, parainfluenza, respiratory syncytial virus).

Bacterial causes are a small minority. They include atypical organisms such as Mycoplasma pneumoniae and Bordetella pertussis, and are generally identified through the specific clinical pattern rather than assumed by default.

Cough is the dominant and defining symptom. It is often productive, though sputum colour does not reliably distinguish bacterial from viral aetiology.

Cough frequently persists for two to three weeks or longer even after resolution of other associated symptoms. This is an important point for patient counselling, given the anxiety that a persistent cough often generates.

Mild constitutional symptoms (low grade fever, malaise) and, occasionally, wheeze from bronchial inflammation may accompany the cough. High fever and significant systemic upset are atypical and should prompt consideration of pneumonia or an alternative diagnosis.

Chest examination is typically unremarkable or reveals scattered wheeze or rhonchi. Focal crackles, dullness to percussion or bronchial breathing would suggest consolidation and pneumonia, which makes them a key distinguishing feature on clinical examination.

Prolonged cough (beyond three weeks) should prompt consideration of alternative diagnoses:

• Pertussis, particularly where there is a preceding history of a paroxysmal or whooping quality to the cough.
• Post infectious cough hyperresponsiveness.
• Asthma.
• Less commonly, an underlying structural or malignant cause, particularly in smokers or older patients.

Diagnosis is clinical. It rests on the characteristic history of cough, generally with a preceding or accompanying upper respiratory tract infection, and examination findings that specifically exclude signs of consolidation.

Chest radiography is not routinely required. Consider it where pneumonia is a clinical possibility (significant fever, focal chest signs, tachypnoea, tachycardia, hypoxia) or where symptoms are atypical, severe or fail to improve as expected.

Consider pertussis testing (nasopharyngeal swab for polymerase chain reaction or culture, or serology depending on the stage of illness) where the clinical picture is suggestive. Suggestive features are a paroxysmal cough, post tussive vomiting, or a whooping quality. Testing also has implications for public health notification and management of contacts.

Sputum culture has limited value in uncomplicated acute bronchitis given the predominantly viral aetiology and is not routinely indicated.

Symptomatic treatment forms the mainstay of management. It includes adequate hydration, rest and simple analgesia or antipyretics as needed. Explain clearly to the patient that cough is expected to persist for a prolonged period even after other symptoms have resolved.

Antibiotics are not routinely indicated for acute bronchitis in an otherwise healthy individual, given the predominantly viral aetiology and the absence of consistent evidence for meaningful clinical benefit.

Reserve antibiotics for:

• Confirmed or strongly suspected pertussis.
• Evidence of underlying chronic lung disease with a significant exacerbation pattern.
• Pneumonia that is diagnosed or strongly suspected.

Cough suppressants and expectorants have limited evidence for benefit. They are used according to patient preference and symptomatic need rather than as an evidence based standard of care.

Bronchodilators may provide symptomatic relief where wheeze is a prominent feature. Evidence for their routine use in uncomplicated bronchitis without an underlying obstructive airway disease is limited.

Clear safety netting advice supports appropriate management of this generally self limiting condition without unnecessary antibiotic use or repeated presentation. It explains that cough may reasonably persist for several weeks. It also gives specific guidance on features that should prompt reassessment (worsening breathlessness, high fever, haemoptysis, or cough persisting beyond three to four weeks without improvement).