What are the key clinical features that differentiate acute bacterial sinusitis from viral sinusitis in adults?

Key clinical features differentiating acute bacterial sinusitis from viral sinusitis in adults include:

• Duration of symptoms: Bacterial sinusitis is more likely if symptoms persist for more than 10 days without improvement, whereas viral sinusitis typically improves within 10 days.
• Symptom progression: A marked deterioration after an initial milder phase (known as "double sickening") suggests bacterial sinusitis.
• Nature of nasal discharge: Discoloured or purulent nasal discharge is more indicative of bacterial sinusitis.
• Severity and localization of pain: Severe localized pain, often unilateral and particularly over the teeth and jaw, favors bacterial sinusitis.
• Fever: A fever greater than 38°C supports a bacterial cause.

In contrast, viral sinusitis usually presents with milder symptoms that improve within 10 days and lacks these features of severity or prolonged duration. Most cases of acute sinusitis are viral and self-limiting, resolving within 12 weeks without antibiotics.

These clinical features guide the decision to consider antibiotics or further investigation, with bacterial sinusitis being less common and often self-limiting but more likely when these features are present.

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