How do you differentiate and manage bacterial vs viral upper respiratory tract infections in patients?

Recognising Bacterial and Viral Upper Respiratory Tract Infection

Distinguish bacterial from viral upper respiratory tract infections based on symptom duration and pattern—not discharge color—with bacterial infection diagnosed when symptoms persist ≥10 days without improvement, worsen after initial improvement ("double-sickening"), or present severely with high fever (≥39°C) and purulent discharge for ≥3-4 consecutive days. 1, 2

Critical Principle: Discharge Color is Misleading

• Purulent (colored, thick) nasal discharge alone does NOT indicate bacterial infection, as viral infections naturally progress from clear to purulent discharge over several days due to neutrophil influx and desquamated epithelium 1, 2
• This is the most common pitfall in clinical practice—colored discharge occurs in both viral and bacterial infections and should never be used as the sole criterion for prescribing antibiotics 1, 2

Viral Upper Respiratory Tract Infection (Viral Rhinosinusitis)

Diagnose viral infection when:

• Symptoms present for <10 days with gradual improvement after days 5-7 1, 2
• Natural progression from clear to purulent discharge that resolves without antibiotics 2
• Fever, if present, occurs early (first 24-48 hours) along with constitutional symptoms 2
• Peak respiratory symptoms (nasal congestion, cough) occur between days 3-6, followed by improvement 2

Management:

• Symptomatic relief ONLY—no antibiotics 1, 2
• Intranasal saline irrigation 1, 2
• Intranasal corticosteroids to reduce inflammation 1, 2
• Analgesics for pain 2

Acute Bacterial Rhinosinusitis (ABRS)

Diagnose bacterial infection when at least ONE of these three patterns is present:

1. Persistent Symptoms (Most Common)

• Symptoms lasting ≥10 days without ANY evidence of clinical improvement 1, 2
• This is the most reliable indicator of bacterial infection 1

2. Severe Onset

• High fever ≥39°C (102°F) AND purulent nasal discharge or facial pain lasting for at least 3-4 consecutive days at the beginning of illness 1, 2
• This pattern suggests bacterial infection from the outset 2

3. Double-Sickening (Worsening After Initial Improvement)

• New onset of fever, headache, or increased nasal discharge following a typical viral URI that initially improved after 5-6 days 1, 2
• This biphasic pattern is highly specific for secondary bacterial infection 1, 2

Cardinal Symptoms Supporting ABRS Diagnosis

When the above timing criteria are met, the presence of these symptoms increases diagnostic confidence:

• Purulent nasal drainage (anterior, posterior, or both)—but remember this alone is insufficient 1
• Nasal obstruction (congestion, blockage, stuffiness) 1
• Facial pain-pressure-fullness (anterior face, periorbital region, or diffuse headache) 1

Important caveat: Facial pain-pressure-fullness in the absence of purulent nasal discharge is insufficient to establish a diagnosis of acute rhinosinusitis 1

Management of Bacterial ABRS

First-Line Antibiotic Therapy

• Amoxicillin with or without clavulanate for 5-10 days for most adults 1, 3
• For children: Amoxicillin alone or in combination with clavulanate 1
• Alternative for penicillin allergy: Doxycycline or respiratory fluoroquinolones 2

Watchful Waiting Option

• For patients with persistent symptoms (≥10 days), observation for 3 days without antibiotics is an option 1
• This approach is NOT appropriate for severe onset or double-sickening patterns 2

Treatment Failure

• Reassess after 3-5 days of antibiotic therapy 2
• If symptoms worsen or fail to improve by 7 days after diagnosis, reassess to confirm ABRS, exclude other causes, and detect complications 1
• Consider broadening antibiotic coverage or switching to a different antimicrobial class 2

Risk Factors for Antibiotic Resistance

Consider these when selecting antibiotics:

• Age <2 or >65 years 2
• Daycare attendance 2
• Recent antibiotic use (within past month) 2
• Recent hospitalization (within past 5 days) 2
• Comorbidities or immunocompromised state 2

For these patients, use 7-10 days of treatment rather than 5-7 days 2

Imaging: When NOT to Order

• Do NOT order plain radiographs or CT scans to differentiate bacterial from viral infection in patients who meet clinical diagnostic criteria 1
• Sinus involvement is common in documented viral URIs, making it impossible to distinguish ABRS from viral infection solely on imaging 1
• Clinical criteria have comparable diagnostic accuracy to sinus radiography 1

Order imaging ONLY when:

• Complications are suspected (orbital involvement, intracranial extension, soft tissue involvement) 1
• Alternative diagnosis is suspected (malignancy, non-infectious causes of facial pain) 1
• Patient has modifying factors predisposing to complications (diabetes, immunocompromised state, history of facial trauma or surgery) 1

Common Pitfalls to Avoid

1. Do NOT prescribe antibiotics based on purulent discharge alone—this is the most common error 1, 2
2. Do NOT continue empiric antibiotics in patients who have failed multiple courses without investigating the underlying cause with nasal endoscopy 4
3. Do NOT use trimethoprim/sulfamethoxazole or azithromycin for penicillin-allergic patients due to high resistance rates 1
4. Do NOT order plain sinus radiographs—they provide inadequate diagnostic information 4

Pediatric Considerations

In children, the diagnostic criteria are similar but with these modifications:

• Cough may be a more prominent symptom than loss of smell 1
• For severe onset, use the same criteria: fever ≥39°C and purulent discharge for ≥3 consecutive days 1
• Intracranial complications (subdural empyema, brain abscess, meningitis) are less common but more serious than orbital complications 1