URI Differentiation

Upper respiratory infections (URIs) encompass a spectrum of conditions affecting the nasal passages, pharynx, larynx, and sinuses. The vast majority (90-98%) are viral, caused by rhinoviruses, coronaviruses, adenoviruses, influenza, and parainfluenza viruses. Viral URIs are self-limiting, typically resolving within 7-10 days, and produce diffuse mucosal inflammation with rhinorrhea, nasal congestion, sore throat, cough, and low-grade fever. Acute bacterial rhinosinusitis (ABRS) develops when sinus ostia become obstructed from viral-induced mucosal edema, impairing mucociliary clearance and creating an anaerobic environment favorable for bacterial proliferation. The most common pathogens are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. ABRS is distinguished from viral URI by duration (symptoms persisting >10 days without improvement), severity (high fever ≥39°C with purulent nasal discharge for ≥3 consecutive days), or double-worsening (initial improvement followed by new onset of fever and worsening symptoms). Group A Streptococcal (GAS) pharyngitis requires differentiation from viral pharyngitis because untreated GAS can cause suppurative complications (peritonsillar abscess, retropharyngeal abscess) and non-suppurative sequelae (acute rheumatic fever, post-streptococcal glomerulonephritis). The modified Centor criteria (McIsaac score) stratify risk: fever >38°C (1 point), absence of cough (1 point), tonsillar...