How do you differentiate and treat viral vs bacterial rhinosinusitis in a patient?

Differentiating Viral vs Bacterial Rhinosinusitis

Diagnose acute bacterial rhinosinusitis (ABRS) only when symptoms persist ≥10 days without improvement OR when symptoms worsen after initial improvement within 10 days ("double sickening"), and reserve antibiotics exclusively for these patients. 1

Clinical Differentiation Criteria

Viral Rhinosinusitis (VRS)

• Duration <10 days with gradual improvement after day 5-7, regardless of nasal discharge color 1, 2
• Symptoms peak at days 3-6 then steadily decline 2
• Purulent (colored) nasal discharge is NOT diagnostic of bacterial infection—it reflects neutrophil presence, which occurs in both viral and bacterial infections 1, 3
• Fever, if present, occurs early (first 24-48 hours) with constitutional symptoms 2
• Self-limited course resolving within 10-14 days 1

Acute Bacterial Rhinosinusitis (ABRS)

Diagnose ABRS when ONE of the following patterns is present: 1

1. Persistent symptoms ≥10 days without any clinical improvement (purulent nasal drainage + nasal obstruction or facial pain/pressure) 1, 2

2. "Double sickening": Initial improvement from viral URI followed by worsening symptoms within 10 days—new fever, increased nasal discharge, or worsening cough 1, 2

3. Severe onset (less commonly used criterion): High fever ≥39°C (102°F) AND purulent nasal discharge or facial pain for ≥3-4 consecutive days at illness onset 2

Key Clinical Pitfall to Avoid

Only 0.5-2% of viral URIs progress to bacterial infection 1, 3—the vast majority of patients with colored nasal discharge have viral illness and do not benefit from antibiotics. 1, 3

Diagnostic Approach

What NOT to Do

• Do NOT obtain sinus radiography or CT for uncomplicated acute rhinosinusitis—imaging cannot distinguish viral from bacterial infection and is not cost-effective 1
• Do NOT use nasal discharge color alone as an indication for antibiotics 1, 2, 3
• Do NOT prescribe antibiotics before day 7-10 unless severe presentation is present 1, 2

When to Image

Obtain CT imaging only when: 1

• Complications suspected (orbital involvement, intracranial extension, severe headache, periorbital edema, diplopia, cranial nerve deficits) 1, 3
• Alternative diagnosis considered (malignancy, invasive fungal sinusitis in immunocompromised patients) 1
• Symptoms persist after maximal medical therapy 1

Treatment Algorithm

For Viral Rhinosinusitis (<10 days, no worsening)

Symptomatic management only—antibiotics are ineffective and harmful: 1

• Analgesics (acetaminophen, ibuprofen) for pain/fever 1
• Intranasal corticosteroids (e.g., fluticasone) for nasal obstruction 1
• Nasal saline irrigation (physiologic or hypertonic) for symptom relief 1
• Oral decongestants if no contraindications (hypertension, anxiety); limit topical decongestants to 3-5 days to avoid rebound congestion 1
• Reassure patient that symptoms typically resolve within 10-14 days 1

For Acute Bacterial Rhinosinusitis (≥10 days OR double sickening)

Two initial management options: 1

Option 1: Watchful Waiting (Preferred for mild-moderate symptoms)

• Observe for additional 3-7 days with symptomatic treatment 1
• Requires assured follow-up to initiate antibiotics if no improvement by day 7 or worsening at any time 1
• Continue analgesics, intranasal corticosteroids, and saline irrigation 1

Option 2: Immediate Antibiotic Therapy

First-line antibiotic: Amoxicillin-clavulanate (not amoxicillin alone—this is a key update from prior guidelines) 1

• Standard dosing: Amoxicillin-clavulanate 500/125 mg three times daily OR 875/125 mg twice daily for 5-10 days 1
• High-dose for resistance risk: Amoxicillin-clavulanate 2000/125 mg twice daily if recent antibiotic use, age <2 or >65 years, daycare exposure, recent hospitalization, or immunocompromised 2

Alternative antibiotics (penicillin allergy): 2

• Doxycycline 100 mg twice daily 2
• Respiratory fluoroquinolone (levofloxacin, moxifloxacin) 2

Avoid azithromycin as monotherapy for ABRS due to high resistance rates in S. pneumoniae 4

Treatment Failure

Reassess at 3-5 days if symptoms worsen or fail to improve: 2

• Confirm ABRS diagnosis and exclude complications 1
• Switch to broader-spectrum antibiotic (high-dose amoxicillin-clavulanate if not already used, or fluoroquinolone) 2
• Consider CT imaging if not previously obtained 1
• Refer to otolaryngology if symptoms persist after maximal medical therapy 1

Evidence Quality Note

These recommendations are based on strong evidence from the American Academy of Otolaryngology-Head and Neck Surgery 2015 updated guidelines 1, which supersede the 2007 guidelines 1 with key changes including extension of watchful waiting to all ABRS patients and preference for amoxicillin-clavulanate over amoxicillin alone. The Infectious Diseases Society of America guidelines 2 provide concordant recommendations with additional detail on resistance patterns.