What distinguishes viral from bacterial sinusitis?

From the Guidelines

Distinguishing Viral from Bacterial Sinusitis

Viral sinusitis is typically self-limiting and managed with symptomatic relief, whereas bacterial sinusitis requires antibiotic therapy. The key distinguishing factors between viral and bacterial sinusitis include the duration and severity of symptoms, with bacterial sinusitis more likely when symptoms persist for more than 10 days without clinical improvement, are severe, or worsen after an initial period of improvement 1, 2, 3, 4, 5.

Clinical Criteria for Differentiation

Clinical guidelines recommend using clinical signs and symptoms to differentiate bacterial from viral causes, as there is no simple and accurate diagnostic test for bacterial sinusitis 1, 2. A bacterial cause is more likely when:

• Symptoms persist for more than 10 days without clinical improvement.
• Symptoms are severe, such as fever >39 °C, purulent nasal discharge, or facial pain lasting for >3 consecutive days.
• Symptoms worsen after an initial period of improvement (double sickening) for more than 3 days.
• New-onset fever, headache, or increased nasal discharge occurs after a typical viral URI that was initially improving 1, 2, 3, 4, 5.

Management Strategies

For bacterial sinusitis, amoxicillin-clavulanate (875mg/125mg twice daily for 5-7 days) or doxycycline (100mg twice daily for 5-7 days) are recommended as first-line treatments 1, 2. In cases of penicillin allergy, azithromycin (500mg once daily for 3 days) or clarithromycin (500mg twice daily for 5-7 days) may be considered as alternative options.

Role of Imaging

Radiographic imaging has no role in ascertaining a bacterial cause and is not helpful in guiding treatment because viral and bacterial causes have similar radiologic features 6. Imaging may be considered when a complication of ABRS or an alternative diagnosis is suspected, such as orbital, intracranial, or soft tissue involvement, or when the patient has modifying factors or comorbidities that predispose to complications.

Key Points

• Viral sinusitis is typically self-limiting and managed with symptomatic relief.
• Bacterial sinusitis requires antibiotic therapy.
• Clinical criteria, such as duration and severity of symptoms, are used to differentiate between viral and bacterial causes.
• Amoxicillin-clavulanate and doxycycline are recommended as first-line treatments for bacterial sinusitis.
• Imaging is not necessary for diagnosis but may be considered in certain situations, such as suspected complications or alternative diagnoses.

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Distinguishing Features of Viral and Bacterial Sinusitis

• The diagnosis of viral and bacterial sinusitis can be challenging due to overlapping symptoms with viral upper respiratory infection and allergy 7.
• Viral illness is the most common predisposing factor for sinusitis, and immune defects may exist in a significant percentage of children 7.
• Bacterial sinusitis is often caused by Streptococcus pneumoniae, Hemophilus influenzae, and Moraxella catarrhalis 7.
• The presence of symptoms such as nasal congestion, sinus headache, and facial pain can indicate either viral or bacterial sinusitis 8.
• A bacterial etiology is more likely if symptoms last longer than 10 days, the temperature is greater than 39°C, or if symptoms worsen after initial improvement 9.

Diagnostic Considerations

• Plain paranasal sinus radiographs are not adequate for determining the extent of involvement in recurrent or chronic sinusitis, and CT scans are often used instead 7.
• The use of antibiotics is not recommended unless symptoms worsen or do not improve after an additional 7 days, as most cases of acute rhinosinusitis are viral 9.
• Rhinovirus infections are the most common cause of viral upper respiratory infections and can progress to bacterial sinusitis and induce chronic rhinosinusitis exacerbations 10.

Treatment Options

• Symptomatic relief of uncomplicated acute rhinosinusitis can be achieved with fluticasone furoate nasal spray, which reduces symptoms compared to placebo 8.
• Antibiotics such as amoxicillin remain the drug of choice for acute bacterial sinusitis, with alternative antibiotic choices available for specific indications 11.
• Treatment options for rhinovirus-associated sinusitis are limited, and further studies are required to develop new strategies targeting rhinovirus-induced chronic rhinosinusitis 10.