Clinical diagnosis and differentiation of acute bacterial from viral rhinosinusitis is based on the characteristic patterns of clinical presentations taking into account duration of symptoms, severity of illness, temporal progression and "double-sickening" in the clinical course
The following clinical presentations (any of the 3) are recommended for identifying patients with acute bacterial vs. viral rhinosinusitis:
- Onset with persistent symptoms or signs compatible with acute rhinosinusitis, lasting for ≥10 days without any evidence of clinical improvement.
- Onset with severe symptoms or signs of high fever (≥39°C) and purulent nasal discharge or facial pain lasting for at least 3 to 4 consecutive days at the beginning of illness.
- Onset with worsening symptoms or signs characterized by the new onset of fever, headache or increased nasal discharge following a typical viral upper respiratory infections that lasted 5-6 days and were initially improving ("double sickening").