What are the symptoms and treatment options for lung infection?

Symptoms of Lung Infection

Lung infections present with cough as the primary symptom, accompanied by at least one additional lower respiratory tract symptom including sputum production, dyspnea, wheeze, or chest discomfort/pain. 1

Core Clinical Manifestations

The defining symptoms of lower respiratory tract infection include:

• Cough (may be productive or non-productive) as the main presenting symptom 1
• Sputum production - often purulent in bacterial infections 2
• Dyspnea (shortness of breath) or tachypnea (rapid breathing) 1
• Chest discomfort or pain 1
• Fever - particularly when lasting more than 4 days, this raises concern for pneumonia 1
• Wheeze in some cases 1

Distinguishing Pneumonia from Simple Respiratory Infection

Suspect pneumonia specifically when you identify new focal chest signs on examination, fever persisting beyond 4 days, or significant dyspnea/tachypnea. 1 The Infectious Diseases Society of America defines pneumonia as new lung infiltrate with supporting clinical evidence including new fever, purulent sputum, leukocytosis, and declining oxygenation 2.

Red Flags Requiring Immediate Evaluation

• Respiratory rate >30 breaths/minute 1
• Hypoxemia (SpO2 <90% or PaO2 <60 mmHg) 1
• New focal chest signs on physical examination 1
• Fever persisting >4 days 1
• Progressive respiratory distress 1

Severity Indicators

Mild to Moderate Infection

• Cough with or without sputum production 1
• Fatigue and generalized weakness 1
• Low-grade fever 1
• Chest discomfort without severe dyspnea 1

Severe Infection Warning Signs

• Increased breathing frequency (>30/min) with inability to maintain adequate oxygenation 1
• Oppression in chest with anhelation (labored breathing) 1
• Persistent high fever 1
• Altered mental status or confusion 1
• Hemodynamic instability 1

Associated Symptoms by Pathogen Type

Bacterial Pneumonia

• Purulent sputum production 2
• Acute onset of symptoms 1
• Leukocytosis on laboratory testing 2
• Pleuritic chest pain in some cases 1

Atypical Pathogens (Mycoplasma, Chlamydia)

• Dry cough predominates 1
• Gradual onset of symptoms 1
• Headache and myalgia may be prominent 1

Viral Infections (Including Influenza)

• Fever with headache 1
• Myalgia (muscle aches) 1
• Sore throat 1
• Dry cough 1

Common Pitfalls to Avoid

Do not diagnose pneumonia in patients lacking new focal chest signs, dyspnea, tachypnea, or fever >4 days. 1 Many patients with simple acute bronchitis present with cough and mild constitutional symptoms but do not require antibiotics or chest imaging 1.

Avoid assuming all respiratory symptoms represent bacterial infection requiring antibiotics. 1 Most acute lower respiratory tract infections in otherwise healthy adults are viral and self-limited 1.

When to Escalate Care

Patients should return immediately if they develop:

• Fever lasting >4 days 1
• Progressive dyspnea or respiratory distress 1
• New focal chest findings 1
• Inability to maintain oxygen saturation 1
• Altered mental status 1

Treatment Considerations

Mild Community-Acquired Pneumonia

For patients appropriate for oral therapy, treatment targets Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, and Chlamydia pneumoniae 1, 3. Azithromycin 500 mg once daily for 3 days or amoxicillin are first-line options 1, 3.

Patients Requiring Hospitalization

Do not use azithromycin monotherapy in patients with moderate to severe illness, bacteremia, significant comorbidities, or those requiring hospitalization. 3 These patients require broader spectrum coverage, often with combination therapy 1.

Acute Bronchitis Without Pneumonia

Antibiotics are not indicated in patients with acute respiratory infection lacking signs of pneumonia, persistent fever, or respiratory distress 1. Symptomatic treatment with dextromethorphan or codeine for troublesome productive cough is appropriate 1.