What is the likely diagnosis for a patient with a 3-day history of upper respiratory infection (URI) symptoms, afebrile, followed by a cough productive of thick green phlegm?

Likely Diagnosis: Acute Viral Bronchitis

The most likely diagnosis is acute viral bronchitis (also appropriately termed a "chest cold"), which is a self-limited viral infection of the lower respiratory tract characterized by cough with or without sputum production lasting up to 3 weeks. 1, 2

Key Diagnostic Reasoning

Why This is Acute Bronchitis and Not Pneumonia

• The absence of fever is critical - it significantly reduces the likelihood of pneumonia, as pneumonia typically presents with acute cough PLUS fever >4 days, new focal chest signs, dyspnea, or tachypnea 2, 3

• The presence of preceding URI symptoms (3 days of "colds") actually argues AGAINST pneumonia as the primary diagnosis, since pneumonia characteristically presents with "fever, absence of URTI symptoms, dyspnea/tachypnea and abnormal chest signs" 2

• Green/colored sputum does NOT indicate bacterial infection - the presence or absence of colored (green) sputum does not reliably differentiate between bacterial and viral lower respiratory tract infections 4, 5

• Viruses cause >90% of acute bronchitis cases, and fewer than 10% have a bacterial etiology 1, 4

Important Differential Considerations

• Rule out pneumonia clinically - pneumonia should only be suspected if the patient has heart rate >100 bpm, respiratory rate >24 breaths/min, fever >38°C, or focal consolidation findings on exam 6, 3

• Rule out asthma - approximately one-third of patients presenting with acute cough are misdiagnosed with acute bronchitis when they actually have acute asthma, particularly if there have been at least two similar episodes in the past 5 years 1

• Rule out the common cold - the diagnosis of acute bronchitis should only be made when there is no clinical or radiographic evidence of pneumonia, and the common cold, acute asthma, or COPD exacerbation have been ruled out 1

When Chest X-Ray is NOT Indicated

A chest radiograph is NOT indicated in this case unless you suspect pneumonia based on specific clinical criteria 2, 3:

• Acute cough PLUS one of: new focal chest signs on examination, dyspnea, tachypnea, or fever >4 days
• Without these findings, chest radiography is neither feasible nor cost-effective, as only 5-10% of patients with acute cough have pneumonia 2

Critical Pitfall to Avoid

Do not label this as "acute bronchitis" when communicating with the patient - instead, call it a "chest cold" or "viral upper respiratory infection." The term "bronchitis" implies a bacterial cause to many patients, leading to inappropriate antibiotic prescribing in 65-80% of cases and unnecessary patient expectations for antibiotics 2, 3, 5

Management Approach

What NOT to Do

• Antibiotics are NOT indicated - this is almost certainly a self-limited viral illness, and antibiotics provide only minimal benefit (reducing cough by about half a day) while causing adverse effects including allergic reactions, nausea, vomiting, and C. difficile infection 2, 3, 4, 5

Recommended Treatment

• Symptomatic relief with first-generation antihistamine/decongestant combination for nasal congestion and cough 2
• Analgesics (acetaminophen or ibuprofen) for any chest discomfort 3
• Adequate hydration and rest 3
• If cough persists beyond 3-5 days and is bothersome, consider inhaled ipratropium bromide as first-line cough suppressant 3

Expected Clinical Course and Red Flags

• Symptoms typically peak at days 3-6 and should begin improving thereafter 3
• Cough may persist for up to 3 weeks (post-infectious cough), which is normal and should be emphasized to the patient 3, 5
• Reassess if symptoms persist >3 weeks without improvement, as this may indicate complications or alternative diagnoses such as asthma, pertussis, or atypical pneumonia 2, 6
• Return immediately if symptoms worsen after initial improvement, new focal chest findings develop, or significant dyspnea occurs 3