Acute Bronchitis: Typical Symptoms and Red Flags
Acute bronchitis presents primarily with acute cough (with or without sputum production) lasting up to 3 weeks, and the diagnosis should only be made after excluding pneumonia, common cold, acute asthma, and COPD exacerbation. 1
Primary Clinical Features
The hallmark symptom is cough that typically persists for 2-3 weeks 2, 3. This may occur with or without phlegm production 1. The cough often begins after an upper respiratory prodrome.
Additional common symptoms include:
- Nasal stuffiness and discharge
- Sore throat
- Sneezing
- Constitutional symptoms (fever, muscle aches, fatigue) 1
- Throat clearing and sensation of postnasal drip 1
Importantly, the color of sputum (including green sputum) does not reliably differentiate viral from bacterial infection 4.
Critical Red Flags Requiring Further Investigation
You must exclude pneumonia before diagnosing acute bronchitis. The absence of ALL four of the following findings makes pneumonia sufficiently unlikely that chest radiography is unnecessary 1:
- Heart rate > 100 beats/min
- Respiratory rate > 24 breaths/min
- Oral temperature > 38°C
- Chest examination findings of focal consolidation, egophony, or fremitus
If any of these are present, obtain a chest X-ray to rule out pneumonia 1.
When to Suspect Alternative Diagnoses
Asthma Misdiagnosis Alert
This is a critical pitfall: approximately one-third of patients initially diagnosed with acute bronchitis actually have acute asthma 1. Even more concerning, 65% of patients with two or more similar episodes of "acute bronchitis" within 5 years have mild asthma 5, 1.
Look for wheezing as a key distinguishing feature suggesting asthma rather than simple bronchitis 1.
Pertussis Consideration
Suspect pertussis when cough persists > 2 weeks and is accompanied by:
- Paroxysmal cough
- Whooping cough
- Post-tussive emesis (vomiting after coughing)
- Recent pertussis exposure 3
Chronic Disease Exacerbations
Consider COPD exacerbation, chronic bronchitis exacerbation, or bronchiectasis exacerbation in patients with known underlying lung disease 5, 1.
Red Flags for Worsening or Complications
If symptoms worsen or fail to improve, reassess and consider targeted investigations 5:
- Chest X-ray
- Sputum culture
- Peak expiratory flow rate
- Complete blood count
- Inflammatory markers (CRP)
High-risk patients requiring closer monitoring include those with:
- Underlying lung disease (COPD, bronchiectasis)
- Congestive heart failure
- Compromised immune system (AIDS, chemotherapy)
- Age ≥ 65 years 1
Duration Expectations
Cough persisting beyond 3 weeks is NOT acute bronchitis 1. At this point, consider alternative diagnoses:
- Post-infectious cough
- Upper airway cough syndrome
- Asthma
- Gastroesophageal reflux disease 1
Key Clinical Pitfall
The most important diagnostic error is failing to distinguish acute bronchitis from the common cold, asthma, and COPD exacerbations 1. The clinical pictures overlap significantly, making prospective longitudinal evaluation essential to determine whether this represents an isolated viral illness or the first manifestation of chronic airway disease 1.