Table 1 Definition of acute, subacute, chronic, recurrent, and recurrent acute sinusitis

Acute sinusitis

1. Sudden onset of ≥ 2 symptoms among nasal obstruction/congestion, nasal discharge, daytime or night-time cough lasting at least 10 days without improvement for a total duration of < 12 weeks/90 days (excluding allergic subjects);

2. Persistent malaise, worsening or new onset of nasal discharge, daytime cough or fever after initial improvement;

3. Severe onset with fever (temperature ≥ 39 °C) and purulent nasal discharge for at least 3 consecutive days.

Subacute sinusitis

Signs/symptoms lasting 4–12 weeks/30–90 days

Chronic sinusitis

Signs/symptoms lasting more than 90 consecutive days

Recurrence

Episode of acute bacterial sinusitis likely lasting less than 30 days, following a previous episode of sinusitis and separated from it by at least 10 days of wellness

Recurrent acute sinusitis

2 episodes of likely acute bacterial sinusitis (at least 3 episodes in 6 months or 4 in 12 months) each lasting less than 30 days.