Pharyngitis Causes and Diagnosis

Viral Etiologies

The American College of Physicians suggests that respiratory viruses account for the majority of pharyngitis cases, including adenovirus, influenza virus, parainfluenza virus, rhinovirus, and respiratory syncytial virus 1, 3
Clinical clues suggesting viral etiology include conjunctivitis, coryza, cough, and diarrhea 3
Epstein-Barr virus (EBV) causes pharyngitis with generalized lymphadenopathy and splenomegaly (infectious mononucleosis) 1, 3

The Infectious Diseases Society of America recommends that Group A β-hemolytic Streptococcus (Streptococcus pyogenes) is the most common bacterial cause and the only form requiring routine antibiotic treatment 1, 2, 6
Clinical features suggesting Group A Streptococcus include sudden onset, fever, headache, nausea/vomiting, tonsillar exudates, tender anterior cervical lymph nodes, absence of cough, age 5-15 years, and winter/early spring presentation 1, 3
Laboratory confirmation (rapid antigen test or throat culture) is required as clinical diagnosis alone is unreliable 1, 3

Groups C and G β-hemolytic streptococci can cause pharyngitis but antibiotic benefit is unproven 1, 6
Very rare but serious bacterial pathogens requiring consideration include Corynebacterium diphtheriae, Neisseria gonorrhoeae, Fusobacterium necrophorum, Arcanobacterium haemolyticum, Francisella tularensis, Yersinia enterocolitica, and mixed anaerobic infections 1, 2, 3, 6

The signs and symptoms of bacterial and viral pharyngitis overlap so broadly that accurate diagnosis on clinical grounds alone is impossible, necessitating laboratory testing when bacterial infection is suspected 1, 2, 3, 6