How do you differentiate between bacterial and viral laryngitis?

Distinguishing Bacterial from Viral Laryngitis

Bacterial laryngitis is exceedingly rare in immunocompetent adults, and the diagnosis should be based primarily on symptom duration and pattern rather than discharge characteristics, as viral laryngitis naturally produces purulent secretions without bacterial infection. 1

Key Clinical Principle

Purulent nasal or throat discharge alone does NOT indicate bacterial infection - this is a critical misconception. Discoloration of secretions is related to neutrophil presence, not bacteria, and occurs naturally during viral infections as part of the inflammatory response. 1, 2

Diagnostic Criteria for Viral Laryngitis

Viral laryngitis is the predominant cause and presents with:

• Symptom duration <10 days with gradual improvement after day 5-7 1, 2
• Natural progression from clear to purulent discharge back to clear/mucoid without antibiotics 1, 2
• Early fever pattern (first 24-48 hours) if present, then resolution while respiratory symptoms continue 1
• Peak symptoms occurring days 3-6, followed by improvement 1, 2
• Hoarseness, cough, sore throat as primary symptoms 1, 3
• Self-limited course with complete resolution within 7-14 days 1

Diagnostic Criteria for Bacterial Laryngitis

Bacterial laryngitis should be suspected ONLY when meeting one of these three specific patterns:

Pattern 1: Persistent Symptoms

• Symptoms lasting ≥10 days WITHOUT any clinical improvement 1, 2
• No worsening required, just lack of improvement beyond 10 days 1

Pattern 2: Severe Onset

• High fever (≥39°C/102°F) AND purulent discharge or facial pain lasting 3-4 consecutive days at illness onset 1, 2
• Patient appears ill 1

Pattern 3: Double Worsening

• Initial improvement after 5-6 days, then new worsening with new fever, headache, or increased discharge 1, 2
• This "double-sickening" pattern is highly specific for bacterial superinfection 2

Special Populations Requiring Different Consideration

Bacterial laryngitis may occur in specific high-risk scenarios:

• Immunocompromised patients (HIV, transplant recipients, chronic steroid use) - may develop atypical mycobacterial or tuberculous laryngitis 1, 4
• Chronic laryngitis >3 weeks in patients already on acid suppression - consider culture-directed therapy 4
• Bacterial tracheitis - presents with stridor, high fever, respiratory distress, and does NOT respond to racemic epinephrine (unlike viral croup) 5

Critical Pitfalls to Avoid

• Do NOT use antibiotics empirically for dysphonia - a Cochrane review found antibiotics ineffective for acute laryngitis in terms of objective outcomes 1
• Do NOT obtain cultures routinely - nasal/nasopharyngeal cultures correlate poorly with actual laryngeal infection 1
• Do NOT rely on physical examination - findings like erythema and edema are nonspecific and present in both viral and bacterial infections 1
• Do NOT obtain imaging for uncomplicated cases - CT/MRI abnormalities persist long after microbiologic resolution and are present in healthy individuals 1

Management Algorithm

For symptoms <10 days (Viral Laryngitis):

• Symptomatic relief only: analgesics, intranasal saline, intranasal corticosteroids 1, 2
• Voice rest for vocal overuse 3
• No antibiotics 1

For symptoms ≥10 days without improvement OR severe onset OR double worsening (Bacterial):

• Consider antibiotic therapy: amoxicillin-clavulanate, doxycycline, or fluoroquinolones for penicillin allergy 2
• Treatment duration: 5-7 days for uncomplicated cases 2

For chronic symptoms >3 weeks in immunocompromised or refractory cases:

• Consider laryngoscopy with culture-directed therapy 4
• Rule out non-infectious causes (reflux, vocal cord lesions, malignancy) 3, 6